#include<iostream>
#include<iomanip>
#include<string>
#include<algorithm>
#include<vector>
#include<set>
#include<list>
#include<queue>
#include<math.h>
#include<bitset>
using ll = long long;
using namespace std;

int main(){
    int t, k;
    cin >> t;
    for (int i = 0; i < t; i++){
        double p, sum1 = 0, r = 1;
        cin >> p >> k;
        for (int j = 0; j < (k-1); j++){
            sum1 += (j+1)*p*r;
            r *= (1 -p);
        }
        cout << fixed << setprecision(6) << sum1 + k*r << endl;
    }
}