def F(f,g):
    lf,lg = len(f),len(g)
    r = [0]*(lf+lg-1)
    for i in range(lf):
        for j in range(lg):
            r[i+j] = (r[i+j]+f[i]*g[j])%MOD
    return r

n,N,*a = map(int,open(0).read().split())
MOD = 10**9+7
f,g = [1],[1]
x = 0
for ai in a:
    g = F(g,[1,-ai])
    x -= pow(ai,N,MOD)
while N:
    h = g[:]
    for i in range(1,len(g),2): h[i] = -h[i]
    f = F(f,h)[N%2:N+1:2]
    g = F(g,h)[:N+1:2]
    N //= 2
print((x+f[0])%MOD)