Katrina is going to order sweatshirts for her girls mentoring group. The sweatshirts will have the group logo printed on the front. Katrina asks two local companies to give her a price. MH Designs will charge $21.50 for each of the sweatshirts. Print Rich will charge $18 for each sweatshirt plus a one-time setup cost of $70. Justify how to determine the number of sweatshirts Katrina would need to order from each company for the costs to be the same. Why?