The population of lengths of aluminum-coated steel sheets is normally distributed with a mean of 30.05 inches and a standard deviation of .2 inches. What is the probability that a sheet selected at random from the population is between 29.75 and 30.5 inches long?

I know the answer is 0.921 but I get stuck after finding the z-scores. I do (29.75-30.05)/.2 = -.15 and 30.5-30.05/2 = 2.25, I see people but P(-.15 < z < 2.25) = .921. How do i enter that into excel, I learned five different formulas just this chapter and I am lost.