**9. **

In 2000 a phone company’s net income was 4300 million dollars and changing at the rate of 800×2 – 4800x + 5200 million dollars per year, where x is the number of years since 2000 (for x ≤ 6). Find a formula I(x) for the phone company’s net income at any time x.

I(x) = ______________________ Use your formula to find their income in 2003. I(3) = $ [removed]million

**10.**

A person can memorize words at the rate of 5/√t words per minute.

(a) Find a formula f(t) for the total number of words that can be memorized in t minutes. [Hint: Evaluate C so that 0 words have been memorized at time t = 0.] f(t) = _______________________ (b) Use the formula that you found in part (a) to find the total number of words that can be memorized in 9 minutes. [removed]words