1. The leakage rate of water from a pipe, $Ll{s}^{-1}$ (litres per second), is directly proportional to the cube root of the flow rate, $sm{s}^{-1}$ (meters per second), which is the speed of the water flowing through the pipe. It was observed that the leakage rate was $0.63l{s}^{-1}$ when the flow rate was $0.729m{s}^{-1}$.

Find the flow rate when the leakage rate is $0.21l{s}^{-1}$.