6- An ice cream shop sells 150 cookies 'n' cream ice cream cakes per month at a price of $40 each. A customer survey indicates that for each $1 decrease in price, sales will increase by 5 cakes. a) Determine a revenue function based on the number of price decreases. b) Determine the marginal revenue for the revenue function developed in part a). c) When is this marginal revenue function equal to zero? What is the total revenue at this time? How can the owners use this information? 7- A sailboat that is coasting with its sails down has velocity v(t) = % meters per second, at time t. a) Give a formula for the acceleration of the sailboat as a function of time. b) When is the sailboat decelerating at 0.5 m/sz