Voice Com desires a profit equal to a 15% rate of return on invested assets of $490,000. Assume that Voice Com, Inc., uses the variable cost concept of applying the cost-plus approach to product pricing. a. Determine the variable costs and the variable cost amount per unit for the production and sale of 6,000 units of cellular phones. b. Determine the variable cost markup percentage for cellular phones. X% c. Determine the selling price of cellular phones. Round to the nearest cent. $ per phone