Two secretarial students, AGYEMANG and IKE, are used- Typewriter dealers. They found that the length of time before a major repair is required on Typewriter sold is normally distributed, with a mean equal to 11 months and a standard deviation of 2 months. If the dealers want only 5% of the cars to fail before the end of the guarantee period, for how many months should the Typewriters be guaranteed? ​