The Strawberry Mansion Company sells its special strawberry pie for $18. The total cost to produce the pie is $10. Of this amount, $2 per unit is selling costs. The total variable cost is $7. The desired profit is $8 per unit. Determine the markup percentage on product cost.

Can someone help me with the math? The equation i have is (desired profit + total selling and administrative expenses) / total poduct cost. I know the desired profit but I dont know how to find the other 2 variables.