Bobby's Red Mill is a mill that sells grains and flours. They are offering a special for shipping. You can ship any package up to 8 pounds for 12.99. If the package exceeds 8 pounds in weight, then the function t = 1.5(p - 8) + 12.99 describes the total cost of shipping, t, in dollars in terms of p, the total number of pounds the package weighs. Which of the following statements best describes this function?