Health plan: The manager of an employee health plan for a firm has studied the balance B, in millions of dollars, in the plan account as a function of t, the number of years since the plan was...

Health plan: The manager of an employee health plan for a firm has studied the balance B, in millions of dollars, in the plan account as a function of t, the number of years since the plan was instituted. He has determined that the account balance is given by the formula

B = 60 + 7t − 50e0.1t .

a. Make a graph of B versus t over the first 7 years of the plan.

b. At what time is the account balance at its maximum?

c. What is the smallest value of the account balance over the first 7 years of the plan?