A local club is selling Christmas trees and deciding how many to stock for the month of December. If demand is normally distributed with a mean of $100$ and standard deviation of $20,$ trees have no salvage value at the end of the month, trees cost $$20,$ and trees sell for $$50$ what is the service level?

Select one:

a$.\mathrm{.}40$

b$.$ unable to determine given the above information

c$.\mathrm{.}20$

d$.\mathrm{.}60$

e$.\mathrm{.}84$