Molly's marbles incurred variable and fixed costs in generating sales for the month of September. Marbles are sold in small bags with each bag considered to be one unit. Information concerning operations for the month of September follows: Total sales: $$50,000.$ Total contribution margin: $30,000.$ Selling price per unit: $5\mathrm{.}00.$ How many units did Molly sell? What was her variable cost per unit? What is the contribution margin per unit?