In the following application problems, assume a linear relationship holds. Exercise 2.57 (Solution on p. 38.) The variable cost to manufacture a product is $25, and the fixed costs are $1200. If z represents the number of items manufactured and y the cost, write the cost function. Exercise 2.58 It costs $90 to rent a car driven 100 miles and $140 for one driven 200 miles. If ar is the number of miles driven and y the total cost of the rental, write the cost function. Exercise 2.59 (Solution on p. 38.) The variable cost to manufacture an item is $20, and it costs a total of $750 to produce 20 items. If a represents the number of items manufactured and y the cost, write the cost function. Exercise 2.60 To manufacture 30 items, it costs $2700, and to manufacture 50 items, it costs $3200. If a represents the number of items manufactured and y the cost, write the cost function.