Consider the the distribution of under-inflated tires on a four-wheel automobile. The mass

density is given by:

p(0) = 0.4, p(1) = p(2) = p(3) = 0.1, p(4) = 0.3

a) Find the expected value and the variance of this distribution.

b) For what proportion of such cars will the number of underinflated tires be within 1 standard deviation of the mean?