1. The average life of a certain type of motor is 10 years, with a standard deviation of 2 years. If the manufacturer is willing to replace only 3% of the motors that fail, how long a guarantee should he offer? Assume that the lives of the motors follow a normal distribution.

2. 10% of the chocolates produced in a factory are defective. In a sample of 1000 chocolates find the probability that the number of defective chocolates are

a) less than 80 b) between 90 and 115 inclusive

c) 120 or more.