We will use binomial distribution in this problem.
The solution would be like
this for this specific problem:
P(default) = p = 4% = 0.04
q = 1-p = 1-0.04 = 0.96
n = 5
P(r) = nCr*q^(n-r)*p^r
Required probability = P(r=2) = 5C2*0.96^3*0.04^2
= 0.0142 OR 1.42%
The probability that at most two customers in the sample will default on their payments is 1.42%.