Caleb is a self$-$employed CPA. He sends his employee, Jeremy, to San Antonio to assist on an audit. Jeremy has expenses for airfare, meals, laundry, lodging, and long$-$distance calls home to his family. Caleb chooses to reimburse Jeremy a set amount per day based upon the location of San Antonio. Which reimbursement method is Caleb using to reimburse Jeremy?

a$.$ The standard federal rate method

b$.$ The high$-$low method

c$.$ Meals and incidental expenses using a per diem amount, with actual expenses for other costs

d$.$ Actual expenses with receipts