Harper works at an electronics store as a salesperson. Harper earns a 6% commission on the total dollar amount of all phone sales she makes, and earns a 5% commission on all computer sales. Harper made a total of $2600 in sales and earned $137 in commission. Write a system of equations that could be used to determine the dollar amount of phone sales Harper made and the dollar amount of computer sales she made. Define the variables that you use to write the system.