Water is poured into a container that has a leak. The mass m of the water is given as a function of time t by m = 5.2t0.8 - 2.6t + 22, with t = 0, m in grams, and t in seconds. In kilograms per minute, what is the rate of mass change at (a) t = 1.6 s and (b) t = 4.6 s?