A cylindrical tank, \(0.3 \mathrm{~m}\) in diameter, drains through a hole in its bottom. At the instant when the water depth is \(0.6 \mathrm{~m}\), the flow rate from the tank is observed to be \(4 \mathrm{~kg} / \mathrm{s}\). Determine the rate of change of water level at this instant.