A motor of power $P_0$ is used to deliver water at a certain rate through a given horizontal pipe. To increase the rate of flow of water through the same pipe $n$ times, the power of the motor is insreased to $P_1$. The ratio of $P_1$ to $P_0$ is :

Question

$$\begin {array} {1 1} (1)\;n:1 & \quad (2)\;n^2:1 \\ (3)\;n^3:1 & \quad (4)\;n^4:1 \end {array}$$