The fixed cost of providing x-ray services is $100,000. The variable cost is $20 per x-ray. What is the total cost of providing 500 x-rays?

The fixed cost of providing x-ray services is $100,000. The variable cost is $20 per x-ray. If 500 x-rays were provided, what is the cost for one x-ray?

A CT scanner has revenues of $700,000 and variable costs of $500,000.What is the contribution margin? (rounded)

Im having trouble understanding on what to do with the number provided in the questions to come up with a correct answer, this will be very much appreciated.