The length of time it takes Revenue Canada to send refunds to taxpayers after the return is received is normally distributed with a mean of 12 weeks and a standard deviation of 3 weeks.

1. What proportion of taxpayers should get sent a refund within 6 weeks.
2. What proportion of refunds will be sent more than 15 weeks after the tax return has been received?
3. How long will it take before 90% of taxpayers have been sent their refunds?