HELP!

If the question is:  How do I enter infinity into my calculator? 

Just answer a ridiculously large number for infinity, such as 999999,

The answer my calculator gives for normalcdf(80.75, 999999, 74, 4) is 0.04575 (approximately).

normal distribution with mean 74 and std. dev. 4

$\text{Normalcdf}(80.75,\infty,74,4) = 0,045753624961741$