4. Consider a function D(t) which describes the total debt of a company (measured in millions of dollars) t months after you become its CEO. (a) For each of the following, write a single sentance describing how the debt is changing: i. D'>0 and D" > 0. ii. D'>0 and D" 0. iv. D' 0 on (0,6) and D' 0 on (8,00). D(6) = 1 and D(8) = 1/2. 0