import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")
debug = lambda x: sys.stderr.write(x+"\n")
writef = lambda x: print("{:.12f}".format(x))


n,pa,pb = input().split()
n = int(n)
pa = float(pa)
pb = float(pb)
A = list(map(int, input().split()))
B = list(map(int, input().split()))
A.sort()
B.sort()
proba = [0]*(1<<n)
probb = [0]*(1<<n)
proba[0] = 1
probb[0] = 1
va = [[0]*n for _ in range(n)]
vb = [[0]*n for _ in range(n)]
for b in range((1<<n)-1):
    l = []
    for i in range(n):
        if b>>i&1==0:
            l.append(i)
    used = n - len(l)
    if len(l)==1:
        psa = [1]
        psb = [1]
    else:
        psa = [pa] + [(1-pa)/(len(l)-1)] * (len(l)-1)
        psb = [pb] + [(1-pb)/(len(l)-1)] * (len(l)-1)
    for ind,i in enumerate(l):
        vva = psa[ind]*proba[b]
        vvb = psb[ind]*probb[b]
        proba[b|(1<<i)] += vva
        probb[b|(1<<i)] += vvb
        va[used][i] += vva
        vb[used][i] += vvb
ans = 0
for i in range(n):
    for j in range(n):
        aa = A[j]
        pa = va[i][j]
        for k in range(n):
            pb = vb[i][k]
            bb = B[k]
            if aa>bb:
                ans += (aa+bb) * pa*pb
print(ans)