Question 1155746
19% of 133 is 25.27, so want no more than 25 to default. 
On calculator use binomcdf (133,.13,26) and probability is 0.9879. ANSWER

Can check by using probability of 26 defaulting or 133C26*.13^26*.87^107=0.0093, then probability of 27 and 28 until the numbers are too small.  But given what 26 is, the other ones will be smaller and the answer is reasonable.  

Normal approximation is np=17.29;  np(1-p)^1/2 is sd =3.88
want probability it is less than 25.
z=(25-17.29)/3.88
=1.99
Probability z>1.99=0.0232
probability z<1.99=0.9768, with error (this is an approximation) but again close to exact answer above.