Question 1180651
Find the probability none is defective
There are 39C4 ways to take the sample
For no defective ones, there are 26C4 possibilities 
so the answer is 1-26C4/39C4
1-0.1818=0.8182

can check
prob of 1 is 13C1*26C3/39C4
=0.4109
-
for 2 it is 13C2*26C2/39C4
=0.3082
-
for 3 it is 13C3*26C1/39C4
=0.0904
-
for 4 it is 13C4/39C4
=0.0087