A surveying instrument makes an error of [math]-2[/math], [math]-1[/math], 0, 1, or 2 feet with equal probabilities when measuring the height of a 200-foot tower.

• Find the expected value and the variance for the height obtained using this instrument once.
• Estimate the probability that in 18 independent measurements of this tower, the average of the measurements is between 199 and 201, inclusive.