From Wikipedia, the free encyclopedia. Phototoxicity, also called photoirritation, is a chemically induced skin irritation, requiring light, that does not involve the immune system. It is a type of photosensitivity. The skin response resembles an exaggerated sunburn.
The contribution margin ratio is the difference between a company's sales and variable expenses, expressed as a percentage. The total margin generated by an entity represents the total earnings available to pay for fixed expenses and generate a profit.
Contribution margin (CM) is the amount by which sales revenue exceeds variable costs. It can be calculated as contribution margin per unit as well as total contribution margin, using the following formulas:Unit CM = Unit Price â Variable Cost per Unit.Total CM = Total Sales â Total Variable Costs.t can be calculated as contribution margin per unit as well as total contribution margin, using the following formulas: Unit CM = Unit Price â Variable Cost per Unit. Total CM = Total Sales â Total Variable Costs.