hi,

Inwould approach this like this:

1. The probability that a lot is rejected is the probability that in a random drawing of six there will be one or more defectives.

2. This probability can be expressed using the probability of anrandomly selected part being defective.

BTW I think in the sum the combination should be (6 n) not (40 n). you could also calculate the probability without the sum as 1 - the probability of 0 defectives out of six.

So, I guess you are almost there, you just need to wrap it up

regrds