The service time of the first service of a BMW car is found to be normally distributed with a mean of 70 minnutes and a variance of 81 minutes.
1. If a customer brings her BMW car for its first service, what is the probability that the car will be ready
within one hour?
2. What is the probability that the job will take more than 90 min?
3. What percentage of the first service will be completed between 50 min and 60 min?
4. The BMW dealer has policy to give its customers a 15% discount on the cost if the first service is not completed within 80 min. From a sample of 80 customers who brought their cars in for the first service, how many are likely to receive the 15% discount?
5. If the dealer wants to ensure that no more than 5% of all its first service will take longer than 80 min, what should the mean service time be?