To encourage motorists to form car pools, the transit authority in a certain metropolitan area has been offering a special reduced rate at toll bridges for vehicles containing four or more persons. When the program began 30 days ago, 157 vehicles qualified for the reduced rate during the morning rush hour. Since then, the number of vehicles qualifying has been increasing at a constant rate, and today 247 vehicles qualified.

a. Express the number of vehicles qualifying each morning for the reduced rate as a function of time, and draw the graph.

b. If the trend continues, how many vehicles will qualify during the morning rush hour 14 days from now?