1. Total annual textbook sales in a certain discipline are normally distributed. Forty-?ve percent of the time, sales are above 671,000 copies, and 10% of the time, sales are above 712,000 copies. Find the mean and the variance of annual sales.
2. Typing speed on a new kind of keyboard for people at a certain stage in their training program is approximately normally distributed. The probability that the speed of a given trainee will be greater than 65 words per minute is 0.45. The probability that the speed will be more than 70 words per minute is 0.15. Find the mean and the standard deviation of typing speed.