Solve the Problem $1200 \mathrm {~L} / \mathrm { hr }$

Solve the problem.
-Twice the water flow in the hot-water pipe is the same as three times the flow in the cold-water pipe. The combined flow is $1200 \mathrm {~L} / \mathrm { hr }$ . What is the flow in each pipe?

A) $400 \mathrm {~L} / \mathrm { hr }$ hot; $600 \mathrm {~L} / \mathrm { hr }$ cold
B) $480 \mathrm {~L} / \mathrm { hr }$ hot; $720 \mathrm {~L} / \mathrm { hr }$ cold
C) $600 \mathrm {~L} / \mathrm { hr }$ hot; $400 \mathrm {~L} / \mathrm { hr }$ cold
D) $720 \mathrm {~L} / \mathrm { hr }$ hot; $480 \mathrm {~L} / \mathrm { hr }$ cold