so I have a stats problem that I can't figure out.

Assume that the distribution of mints produced with a label weight of 20.4 is N(21.34, .16)

15 mints are selected independently. let Y be the number of those that weight less than 20.857 g. determine P[Y≤2].

The chapter for this is only about three paragraphs long and doesn't touch on this type of problem...any help?

thanks in advance!