#include <bits/stdc++.h>
using namespace std;

int main() {
	int t;
	cin >> t;
	for (int i = 0; i < t; i++) {
		double p;
		int k;
		cin >> p >> k;
		double ans = 0;
		double tmp = 1;
		for (int j = 1; j < k; j++) {
			ans += j * tmp * p;
			tmp *= (1 - p);
		}
		ans += tmp * k;
		cout << fixed << setprecision(15);
		cout << ans << endl;
	}
}