Just simple multiplication. 3 times the expectation that he will have to get it repaired in one year.
d)How many times should the company expect to have to get this computer repaired over the three-year term of the lease?
Do you know how to do linear transformations of means, std, variance, etc.? That's all you are doing here. Multiplying by a scalar 3. However the effect that is has on the mean (just multiply by three), is not the same as it has on the std and variance.
e)What is the standard deviation of the number of repairs that be required during the three-year lease period? On what assumption does your calculation rest. Do you think that this assumption is reasonable?
If the printer fails, is that going to affect the computer failing?
f)The service contract for the printer estimates a mean annual cost of $120 with standard deviation of $30. What is the expected value and standard deviation of the total cost for the service contracts on computer and printer? On what assumption does your calculation rest?
Yes you do. You already calculate the EXPECTED cost of one, and they give you the EXPECTED cost of the other.
g)Which service contract should the company expect to cost more each year? How much more? With what standard deviation?