def get(n,p):
    res = [[0.0]*n for _ in range(n)]
    for j in range(n):
        dp = [0.0]*n # i 回目, j が k 枚目
        dp[j] = 1.0
        for i in range(n-1):
            ndp = [0.0]*n
            q = (1.0-p)/(n-i-1)
            for k in range(n):
                ndp[k] += dp[k]*q*(n-i-1-k)
                if k: ndp[k-1] += dp[k]*(1.0 - q*(n-i-k))
                res[i][j] += dp[k]*(p if k==0 else q)
            dp = ndp
        res[n-1][j] = sum(dp)
    return res

n,pa,pb = input().split()
n,pa,pb = int(n), float(pa), float(pb)
a = sorted(map(int,input().split()))
b = sorted(map(int,input().split()))
ra,rb = get(n,pa),get(n,pb)
ans = 0.0
for s in range(n):
    for i,ai in enumerate(a):
        for j,bj in enumerate(b):
            if ai > bj:
                ans += ra[s][i]*rb[s][j]*(ai+bj)
print(ans)