Question 1187691
The mean is 17 pounds (a+b)/2
between 15-16.5 pounds is 1.5 pounds, and the total range is 6 pounds. Probability is 0.25
fewer than 15 pounds is probability 1/6 (from 14-15 only).
at least 18 pounds is probability 1/3 or 2/6 (from 18-20 pounds.
sd is sqrt((b-a)^2/12)
that is sqrt(36/12) or sqrt (3), or 1.732 pounds 
variance is sd ^2 or 3 pounds^2