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 = 4.7t0.8 - 2.9t + 19, with t ? 0, m in grams, and t in seconds. (a) At what time is the water mass greatest, and (b) what is that greatest mass? In kilograms per minute, what is the rate of mass change at (c) t = 1.8 s and (d) t = 5.4 s?