## https://yukicoder.me/problems/no/2651

MOD = 998244353

def solve(N, xy):

    z2_list = []
    for x, y in xy:
        x_ = (pow(x, 2, MOD) - pow(y, 2, MOD)) % MOD
        y_ = (x * y) % MOD
        y_ *= 2
        y_ %= MOD
        z2_list.append((x_, y_))
    
    z_abs_list = []
    for x, y in xy:
        s = pow(x, 2, MOD)
        s += pow(y, 2, MOD)
        s %= MOD
        z_abs_list.append(s)

    # 1 / |z|^2 の累積和計算
    cum_inv_z_abs2_list = [0] * N
    cum_inv_z_abs2 = 0
    for i in range(N):
        cum_inv_z_abs2_list[i] = cum_inv_z_abs2
        cum_inv_z_abs2 += pow(z_abs_list[i], (MOD - 2), MOD)
        cum_inv_z_abs2 %= MOD

    # |z|^2 の累積和計算
    cum_z_abs2_list = [0] * N
    cum_z_abs2 = 0
    for i in range(N):
        cum_z_abs2_list[i] = cum_z_abs2
        cum_z_abs2 += z_abs_list[i]
        cum_z_abs2 %= MOD
    
    # cum_a_list = 
    cum_a_list = [0] * N
    cum_a = 0
    for i in range(N):
        cum_a_list[i] = cum_a
        a = z2_list[i][0]
        a *= pow(z_abs_list[i], MOD - 2, MOD)
        a %= MOD
        cum_a += a
        cum_a %= MOD

    cum_b_list = [0] * N
    cum_b = 0
    for i in range(N):
        cum_b_list[i] = cum_b
        a = z2_list[i][1]
        a *= pow(z_abs_list[i], MOD - 2, MOD)
        a %= MOD
        cum_b += a
        cum_b %= MOD
    
    answer = 0
    for i in range(N):
        ans = (z_abs_list[i] * cum_inv_z_abs2_list[i]) % MOD
        ans += (cum_z_abs2_list[i] * pow(z_abs_list[i], MOD - 2, MOD)) % MOD
        ans %= MOD
        ans_re1 = (z2_list[i][0] * pow(z_abs_list[i], MOD - 2, MOD)) % MOD
        ans_re1 *= cum_a_list[i]
        ans_re1 %= MOD
        ans_re2 = (z2_list[i][1] * pow(z_abs_list[i], MOD - 2, MOD)) % MOD
        ans_re2 *= cum_b_list[i]
        ans_re2 %= MOD

        ans_re = (ans_re1 + ans_re2) % MOD
        ans_re *= -2
        ans_re %= MOD

        answer += ans
        answer %= MOD
        answer += ans_re
        answer %= MOD
    return answer




def main():
    T = int(input())
    answers = []
    for _ in range(T):
        N = int(input())
        xy = []
        for _ in range(N):
            x, y = map(int, input().split())
            xy.append((x, y))
        ans = solve(N, xy)
        answers.append(ans)

    for ans in answers:
        print(ans)







if __name__ == "__main__":
    main()