Aiman Company is a supplier of custom-built refrigerators. It gathered the following monthly data relating to units sold and total selling expense: Month Units sold Total selling expense March 4 $1,900 April 7 2,400 May 5 1,800 June 6 2,100 July 8 2,400 August 10 2,800 September 3 1,300 Instructions: (2+1+1=4) a. Using the high-low method, estimate the fixed cost and the variable cost of total selling expense. b. Express the variable and fixed costs in the form Y= a + bx. c. If the company sold 15 refrigerators in October, what would be the total selling expense for that month