The book Code Complete by Steve McDonnell estimates that there are 15 to 50 errors per 1,000 lines of delivered code for computer programs.

Assume that for a particular software package, the error rate is 25 per 1,000 lines of code and that the number of errors per 1,000 lines of code follows a Poisson distribution.

a. What is the probability that a portion of code for this software package that contains 250 lines of code contains no errors?

b. What is the probability of there being exactly 30 errors in 1,000 lines of code?

c. What is the probability of more than 3 errors in 100 lines of code?

d. What is the expected number of errors in a portion of code that contains 25,000 lines of code?