Alake near the arctic circle is covered by a thick sheet of ice during the cold winter months. when spring arrives, the warm air gradually melts the ice, causing its thickness to decrease at a rate of 0.2 meters per week. after 7 weeks, the sheet is only 2.4 meters thick. let s(t)s(t) denote the ice sheet's thickness ss (measured in meters) as a function of time tt (measured in weeks).