I am doing a case study in GCU MGT655. This is the question. If the specification is such that no washer should be greater than 2.

I am doing a case study in GCU MGT655. This is the question. If the specification is such that no washer should be greater than 2.4mm assuming that the thicknesses are distributed normally what fraction of the output is expected to be greater than this thickness? There are 40 numbers with all of them 2.4mm or less so Im not sure where to start