A factory produces, fuses, which are packaged in boxes of 10. Three fuses are selected at random from each box for inspection. The box is rejected if...

A factory produces, fuses, which are packaged in boxes of 10. Three fuses are selected at random from each box for inspection. The box is rejected if at least one of these three fuses is defective.

a if a particular box contains 5 defective fuses, in how many samples will there be exactly 2 defective fuses?

b what is the probability that a box containing 5 defective fuses will be rejected?