The STC Supply manufactures memory cards that sell to wholesalers for $4.00 each Variable and fixed costs are as follows: STC Supply produced and sold 20.000 cards during October 2014. Assume the company had no beginning or ending inventories. Required: a. Prepare a contribution income statement for the month of October. b. Determine STC Supply's monthly break-even point in units. c. Determine the effect on monthly profit of a 1,000 unit increase in monthly sales. d. If STC Supply is subject to an income tax of 40 percent, determine the dollar sales volume required to earn a monthly after-tax profit of $30,000