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.
Contribution margin ratio measures the percentage of sales that would increase net income. To calculate it, divide contribution margin by sales, either in total or per unit: Suppose a gadget selling for $100 per unit brings in $40 per unit of contribution margin.
The first variable you need to find for the contribution margin equation is its unit revenue â in other words, the price it's sold for. The confusing term unit revenue is used in economics because the product's price is equal to the revenue generated by the sale of a single product (or one unit).ontribution margin is a concept often used in a branch of managerial accounting known as cost-volume-profit (CVP) analysis. A single product's contribution margin is given with the formula P-V, where P is the cost of the product and V is its variable cost.