#include <bits/stdc++.h>

using namespace std;

typedef long long   LL;
#define pii         pair<int,int>
#define pll         pair<LL,LL>
#define vi          vector<int>
#define SYNC        ios_base::sync_with_stdio(0)
#define CT          cin.tie(0)
#define sf(a)       scanf("%d", &a)
#define sff(a, b)   scanf("%d %d", &a, &b)
#define sfff(a,b,c) scanf("%d %d %d", &a, &b, &c)
#define debug       printf("Here\n")
#define PI          acos(-1)
#define all(x)      (x.begin(),x.end())
#define mem(x, val) memset((x),val,sizeof((x)))
#define xx          first
#define yy          second
#define pb          push_back
#define _max(a,b,c) max(a, max(b, c))
#define _min(a,b,c) min(a, min(b, c))
#define INF         INT_MAX
#define MOD         1000000007
#define NN          1005

int setBit(int n, int pos) { return n = n | (1 << pos); }
int resetBit(int n, int pos) { return n = n & ~(1 << pos); }
bool checkBit(int n, int pos) { return (bool)(n & (1 << pos)); }

double dp[NN][NN];

double call(int n, int m, int tot) {
    if(n == 0) return 1;
    if(m == 0 && n == 1) return 0;
    if(dp[n][m] != -1) return dp[n][m];
    double ret = 0;
    if(m) ret += ((double) n / (double)tot) * ((double)m / ((double)tot - 1.0)) * call(n, m - 1, tot - 1);
    if(n > 1) ret += ((double) n / (double)tot) * ((double)n - 1.0) / ((double)tot - 1.0) * call(n - 2, m, tot - 2);
    return dp[n][m] = ret;
}

int main() {
    for(int i = 0; i < NN; i++)
        for(int j = 0; j < NN; j++)
            dp[i][j] = -1;
    int t, d, T, tt = 1;
    sf(T);
    while(T--) {
        sff(t, d);
        printf("Case %d: %.10lf\n", tt++, call(t, d, t + d + 1));
    }
    return 0;
}