t = int(input())

while t >= 1:
    t -= 1

    n, m = map(int, input().split())
    a = [0]*n; b =[0]*m

    inp = input().split()
    for i in range(0, n):
        a[i] = int(inp[i])

    inp = input().split()
    for i in range(0, m):
        b[i] = int(inp[i])

    a.sort(); b.sort(reverse=True)

    ans = 0
    for i in range(0, min(n,m)):
        if a[i] >= b[i]:
            break
        ans += b[i]-a[i]

    print(ans)