(1) The opposite of at least one qualification is all unqualified, and the probability of all unqualified is: 0.2*0.2*0.2*0.2=0.00 16.

So at least one qualified probability is: 1-0.00 16=0.9984.

(2) The value of the unqualified number x is: 0, 1, 2.

p(X = 0)= 17/20 * 16/ 19 = 68/95

p(X = 1)= 17/20 * 3/ 19+3/20 * 17/ 19 = 5 1/ 190

p(X = 2)= 3/20 * 2/ 19 = 3/ 190

So e (x) = 51190+2 * 3/190 = 57/190.

The rejection probability p = 51190+3/190 = 27/95.