A store orders 600 units of a product every 3 months. If the product is steadily depleted to 0 by the end of each 3 months, the inventory on hand I at any time t during the year is shown in the following figure:

(A) Write an inventory function (assume that it is continuous) for the first 3 months. [The graph is a straight line joining (0, 600) and (3, 0).]
(B) What is the average number of units on hand for a 3- month period?