Gary C'Toole is a new accountant with Blue Spruce Company. Blue Spruce purchased merchandise on account for $$57,600.$ The credit

terms are $\frac{2}{10},\frac{n}{30}.$ Gary has talked with the company's banker and knows that he could earn $5\%$ on any money invested in the

company's money market account.

$($a$)$

Should Gary pay the invoice within the discount period or should he keep the $$57,600$ in the money market for $20$ days

and pay at the end of the credit period? $($Use $360$ days in a year.$)$