To calculate the selling price of the item, you must apply the following formula:
Selling price=(Markup/Product costx100%)+Product cost
You have that:
Markup=40%
Product cost=$8.00
Given these values, you only have to substitute them into the formula of Selling price:
Selling price=(Markup/Product costx100%)+Product cost
Selling price=(40%/$8.00x100%)+$8.00
Selling price=$3.20+$8.00
Selling price=$11.20