( a) "Lion" restaurant has a reputation for good food. Owner of the restaurant boasts that on a Friday night, average arrivals of group of customer per hour is 15. What is the probability that at least 3 groups of customers will arrive in 10 minutes?

( b) Accounts division of Kumara company has compiled data on the age of accounts receivable. The data collected indicate that the age of accounts follows a normal distribution, with mean of 32 days and a standard deviation of 6 days.

(i) The company accountant is interested in sending reminder letters to the oldest 8% of accounts. How many days old should an account be before a reminder letter is sent?

(ii) The company accountant would like give a 5% discount to those accounts which pay their balance by 18th day. What percentage of the accounts will receive the discount