What is the intensity, in watts per square meter, of a laser beam that is 90.0% absorbed by a 2.15-mm diameter spot of cancerous tissue and must deposit 525 J of energy to it in a time period of 4.2 s?

Kiloleter, mega leterhope this !

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other

The answer is d, you can easily test a theory! hope i you : )