Trent needed pinnies for the lacrosse team to wear during scrimmages and called a local supplier and was told that he could purchase pinnies for $10 each. He asked the supplier to hold five pinnies for him to purchase. However, when Trent arrived at the store a few days later, he found the price of the pinnies had increased to $12. Due to the price increase, Trent only purchased four pinnies. Using the mid-point formula, Trent's own-price elasticity of the pinnies is __________.

• a.)
• b.)
• c.)
• d.)

-1.22

3

-2

4.5