Can someone help me to answer this question, please and explain it.

This is calculus 1

Task 1: The Stock Market crash took place on September 29, 2008. The trend of the stock price (scaled from the base value) both before and after the day market crashed can be described as f (t) = -at - - where a and b are both positive constants and t is the time (in days) from the day of the market crash. a. Find the critical value(s) of f. (Your answer will be in terms of a and b.) b. Over what interval(s) is the stock price increasing