The respiratory rate per minute in newborns varies according to a distribution that is approximately Normal with mean 50 and standard deviation 5.

The proportion of observations from a standard Normal distribution that take values less than 1.15 is about
(a)

0.1251.
(b)

0.8531.
(c)

0.8749.

The answer is C, but I'm unsure how to do this on a TI-89 using the normalCDF function