#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001



int main(){
	
	int _t;
	cin>>_t;
	
	rep(_,_t){
		
		long double p;
		cin>>p;
		int K;
		cin>>K;
		long double c  = 1.0;
		long double ans = 0.0;
		for(int i=1;i<=K;i++){
			ans += c*p*i;
			c *= 1.0-p;
		}
		ans += c*K;
		cout<<fixed<<setprecision(15)<<ans<<endl;
	}
	
	return 0;
}