To raise money for charity, a group of students decide to sell designer T-shirts. The cost to rent the machine that sells that prints the T-shirts is $172. The cost to buy and print the design on each T-shirt is $13. The students plan to sell the T-shirts for $17 each. Let X represent the number of T-shirts. How many T-shirts must be sold before the students start making profit?

Based on the given roots and their multiplicities, the function is made of the following factors:
f(x) = x (x + 3)^2 (x - 1) (x - 3)^2

The roots represent the point in the graph where they touch the x-axis. With the given condition that the function has a positive leading coefficient and is of even degree, the group of the function touches the x-axis at the roots and is curved upwards.