Sam borrows $10,000 from a bank at an interest rate of 9% and pays back the loan continuously at a rate of N dollars/year. Let P(t) denote the amount still owed at time t.
(a) Explain why P(t) satisfies the differential equation
(b) How long will it take Sam to pay back the loan if N = $1,200?
(c) Will he ever be able to pay back the loan if N = $800?