Suppose a software company finds that the number of errors in its software per 1,000 lines of code is described by a Poisson distribution. Furthermore, it is found that there is an average of four errors per 1,000 lines of code. Letting x denote the number of lines of code between successive errors:
a. Find the probability that there will be at least 400 lines of code between successive errors in the company's software.
b. Find the probability that there will be no more than 100 lines of code between successive errors in the company's software.