Joseph purchased a laptop that regularly sold for w dollars but was on sale at 10% off. He hac pay t dollars for sales tax He bought it on the installment plan and had to pay 15% of the tot cost with tax as a down payment. His monthly payments were m dollars per month for three years a. Write expressions for the amount of the discount and the sale price, b. Write expressions for the to:al cost of the laptop, with tax, and the down payment. What was the total of all of the monthly payments? What was the total he paid for the widget on the installment plan? d. What was the finance charge?