12. An online clothing company sells custom sweatshirts. The company
charges $6.50 for each sweatshirt and a flat fee of $3.99 for shipping.
a. Write a linear function in the form y = mx + b that represents the total
cost, y, in dollars, for a single order of x sweatshirts.
b. Describe how the linear function would change if the shipping
charge applied to each sweatshirt.