Chapter 1, Problem 333RE

For the following problems, consider a restaurant owner who wants to sell T-shirts advertising his brand. He recalls that there is a fixed cost and variable cost, although he does not remember the values. He does know that the T-shirt printing company charges $440 for 20 shirts and $1000 for 100 shirts.

333. Tire population can be modeled by $P\left(t\right)=82.5-67.5\cos \left[\left(\pi /6\right)t\right]+t$ , where f is time in months (t = 0 represents January 1) and P is population (in thousands). During a year, in what intervals is the population less than 20,000? During what intervals is the population more than 140,000?