The profit that is gained by the company for selling a unit is equal to the difference between the revenue and total cost. In this item the revenue is given to be $45 and the profit is $10. To answer this item, we let x be the cost such that,
45 - c = 10
Simplifying,
c = 45 - 10
Further simplification will lead us to,
c = 35
Answer: $35.