Question 1176464
a. is correct
b is (4C1)(4C3/8C4=16/70 correct
c. what is the probability NONE is defective, which is (4/8)(3/7)(2/6)(1/5)=24/1680=(1/70)
that is also (4C0)*(4C4)/8C4=1/70
at least one is defective is the complement of 1/70 or 69/70.