The diameters of screws produced by a particular machine follow a normal
distribution with mean 1.35 cm and standard deviation 0.04 cm. Screws with diameters less than 1.25 cm are rejected for being too small, while those with diameters more than dem are rejected for being too large.
Estimate the proportion of screws that are too small.
You can play around with Z table stuff at
davidmlane.com/hyperstat/z_table.html