An automatic machine in a factory produces parts for a medical device. Most of the

time $(90\%,$ according to long$-$term records$),$ it produces $95\%$ good parts, while the remaining

parts must be scrapped. The rest of the time, the machine slips into a less productive mode and

only produces $70\%$ good parts. The inspector in charge of this machine has decided to

periodically inspect the most recent dozen parts produced, and to adjust the machine if they

believe that it is not working well.