A wholesale garden center estimates that it will sell N units of a basket of three potted amaryllises after spending a dollar on advertising, where N(a) = - a2 + 300a + 6, ‰¤ a ‰¤ 300, and a is measured in thousands dollars.

(a) Graph the function using a graphing calculator.
(b) Use the MAXIMUM feature to find the relative maximum.
(c) For what advertising expenditure will the greatest number of baskets be sold? How many baskets will be sold for that amount?