627 B | 627 chars
import sys
from math import sqrt, pi, sin, factorial
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = " " : [*map(int,inp().split(x))]
mfi = lambda x = " " : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
ans = 0
n, k = mii()
s = inp()
l = [inp() for _ in range(n)]
for i in range(k):
for j in range(n):
if l[j][i] == s[i]:
break
else:
ans += 1
return f"{ans}/{k}"
if __name__ == "__main__":
tc = ii()
for t in range(1, tc+1):
ret = solve()
p(f"Data Set {t}:")
p(ret)
p()