5. (6 PTS) If the total revenue (in dollars) received from the sale of a items is given by R(x) = 25 In(1 + 4x), while the total cost (in dollars) to produce r items is C(x) = , find the following: (a) The profit function. (b) The marginal profit function. (c) How fast the profit is changing when 2 items are sold? Round your final answer to two decimal places if necessary and label your answer. 6. (6 PTS) Find for the equation ry + 21 =1 -3y. Simplify your answer if possible.4. (6 PTS) The temperature T (in degrees Farenheit) of a person during an illness is given by 12h 1 (0) = 7215 +98.6 where h is the number of hours after diagnosis. (a) Find the rate of change of the temperature. Simplify your answer. (b) Find the rate of change of the temperature at h = 2. Round your final answer to two decimal places if necessary and label your