import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }

string COLOR(string s = "") { return "\x1b[" ~ s ~ "m"; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


struct ModInt(uint M_) {
  import std.conv : to;
  alias M = M_;
  uint x;
  this(ModInt a) { x = a.x; }
  this(uint x_) { x = x_ % M; }
  this(ulong x_) { x = cast(uint)(x_ % M); }
  this(int x_) { x = ((x_ %= cast(int)(M)) < 0) ? (x_ + cast(int)(M)) : x_; }
  this(long x_) { x = cast(uint)(((x_ %= cast(long)(M)) < 0) ? (x_ + cast(long)(M)) : x_); }
  ref ModInt opAssign(T)(inout(T) a) if (is(T == uint) || is(T == ulong) || is(T == int) || is(T == long)) { return this = ModInt(a); }
  ref ModInt opOpAssign(string op, T)(T a) {
    static if (is(T == ModInt)) {
      static if (op == "+") { x = ((x += a.x) >= M) ? (x - M) : x; }
      else static if (op == "-") { x = ((x -= a.x) >= M) ? (x + M) : x; }
      else static if (op == "*") { x = cast(uint)((cast(ulong)(x) * a.x) % M); }
      else static if (op == "/") { this *= a.inv(); }
      else static assert(false);
      return this;
    } else static if (op == "^^") {
      if (a < 0) return this = inv()^^(-a);
      ModInt b = this, c = 1U;
      for (long e = a; e; e >>= 1) { if (e & 1) c *= b; b *= b; }
      return this = c;
    } else {
      return mixin("this " ~ op ~ "= ModInt(a)");
    }
  }
  ModInt inv() const {
    uint a = M, b = x; int y = 0, z = 1;
    for (; b; ) { const q = a / b; const c = a - q * b; a = b; b = c; const w = y - cast(int)(q) * z; y = z; z = w; }
    assert(a == 1); return ModInt(y);
  }
  ModInt opUnary(string op)() const {
    static if (op == "+") { return this; }
    else static if (op == "-") { ModInt a; a.x = x ? (M - x) : 0U; return a; }
    else static assert(false);
  }
  ModInt opBinary(string op, T)(T a) const { return mixin("ModInt(this) " ~ op ~ "= a"); }
  ModInt opBinaryRight(string op, T)(T a) const { return mixin("ModInt(a) " ~ op ~ "= this"); }
  bool opCast(T: bool)() const { return (x != 0U); }
  string toString() const { return x.to!string; }
}

enum MO = 998244353;
alias Mint = ModInt!MO;


void main() {
  debug {{
    int[] f(int m) {
      return m ? (0.repeat(m-1).array ~ [-1, 1]) : [1];
    }
    int[] add(const(int[]) ps, const(int[]) qs) {
      auto rs = new int[max(ps.length, qs.length)];
      foreach (i, p; ps) rs[i] += p;
      foreach (j, q; qs) rs[j] += q;
      return rs;
    }
    int[] mul(const(int[]) ps, const(int[]) qs) {
      auto rs = new int[ps.length + qs.length - 1];
      foreach (i, p; ps) foreach (j, q; qs) rs[i + j] += p * q;
      return rs;
    }
    // foreach (a2; 0 .. 5 + 1) foreach (a1; 0 .. 1 + 1) {
    foreach (a2; 1 .. 5 + 1) foreach (a1; 1 .. 1 + 1) {
      int[] ans;
      foreach (c0; 0 .. a2 + 1) {
        const c1 = a2 - c0;
        ans = add(ans, mul(mul(f(c0), f(c1)), f(a1 + c1)));
      }
      writeln([a1, a2], ": ", ans);
    }
    // foreach (a3; 0 .. 5 + 1) foreach (a2; 0 .. 5 + 1) foreach (a1; 0 .. 1 + 1) {
    foreach (a3; 1 .. 5 + 1) foreach (a2; 1 .. 5 + 1) foreach (a1; 1 .. 1 + 1) {
      int[] ans;
      foreach (c0; 0 .. a3 + 1) foreach (c1; 0 .. a3 - c0 + 1) {
        const c2 = a3 - c0 - c1;
        foreach (d0; 0 .. (a2 + c2) + 1) {
          const d1 = (a2 + c2) - d0;
          ans = add(ans, mul(
            mul(
              mul(mul(f(c0), f(c1)), f(c2)),
              mul(f(d0), f(d1))
            ),
            f(a1 + c1 + d1)));
        }
      }
      writeln([a1, a2, a3], ": ", ans);
    }
  }}
  
  try {
    for (; ; ) {
      const numCases = readInt;
      foreach (caseId; 0 .. numCases) {
        const N = readInt;
        const Mint K = readInt;
        auto A = new long[N + 1];
        foreach (i; 1 .. N + 1) {
          A[i] = readLong;
        }
        
        Mint ans = 1;
        Mint kk = 1;
        foreach (i; 1 .. N + 1) {
          kk *= K;
          ans *= (kk - 1);
        }
        long sum;
        foreach (i; 1 .. N + 1) {
          sum += (A[i] - 1) * i;
          sum = (sum < 1) ? sum : (1 + (sum - 1) % (MO - 1));
        }
        ans *= Mint(K)^^sum;
        writeln(ans);
      }
    }
  } catch (EOFException e) {
  }
}