AMC 8 1996 Problem 7

Brent has goldfish that quadruple (become four times as many) every month, and Gretel has goldfish that double every month. If Brent has 4 goldfish at the same time that Gretel has 128 goldfish, then in how many months from that time will they have the same number of goldfish? $\text{(A)}\ 4 \text{(B)}\ 5 \text{(C)}\ 6 \text{(D)}\ 7 \text{(E)}\ 8$