The contribution margin per unit is equal .6 to the (1 (1 ) sales price per unit minus the variable .cost per unit .aftertax profit per unit variable cost per unit minus the fixed .cost per unit pretax profit per unit sales price per unit minus the total costs per unit The IRR that causes the net present value 7 of the differences between two project's cash flows to equal zero is called the 1 (1 ) .break-even rate .present value rate crossover rate