The following information on costs and activity are given for Underwood Enterprises. Using the high-low method, calculate the variable cost per unit. Total cost # of units January $ 8,300 15,000 February $ 10,800 20,000 March $ 7,200 12,000 April $ 9,500 18,000 Select one: $0.60 $1.40 $0.45 $0.55 $0.40 $0.52