Area between curves

a: Suppose your daily revenue from selling used DVDs is

R(t) = 100 + 10t (0 t 5)

dollars per day, where t represents days from the beginning of the week, while your daily costs are

C(t) = 65 + 5t (0 t 5)

dollars per day. Find the area between the graphs of R(t) and C(t) for 0 t 5. What does your answer represent?

b: Suppose your annual income is

I(t) = 63,000 + 2,000t (0 t 3)

dollars per year, where t represents the number of years since you began your job, while your annual expenses are

E(t) = 52,000 + 1,500t (0 t 3)

dollars per year. Find the area (in dollars) between the graphs of I(t) and E(t) for 0 t 3. What does your answer represent?