for _ in range(int(input())):
    p, K = input().split()
    p = float(p)
    K = int(K)
    
    dp = [0] * (K + 1)
    dp[0] = 0
    wa = 0
    for i in range(1, K):
        dp[i] = (1 - wa) * p
        wa += dp[i]
    
    dp[K] = (1 - wa)
    
    ans = 0
    for i in range(1, K + 1):
        ans += i * dp[i]
    print(ans)