this question is from elementary probability theory

2.5 An executive in a company is very concerned about the possibility of an incorrect cost estimate on the various jobs on which he bids. The com- pany practice in estimating job costs is to have one engineer estimate the cost for an entire project and then have two other engineers go over the figures independently. The probablety that the first engineer will make a mistake is only 5%, because he is very careful when he figures an entire project cost. The two engineers who check the figures each has a proba- bility of catching all mistakes of only 60%, because they do not devote much time to the job and take many estimates for granted. (a) What is the probability that the executive will base his bid on an incorrect cost estimate? (b) On the average, how many cost estimates will be incorrect per 1000? (c) What type of probability is stated in part (a)? (d) What is the probability that the first engineer will make a mistake that will be detected by later investigation