4.91 Students in a college were classified according to years in school (X) and number of visits to a museum in the last year (Y = 0 for no visits, 1 for one visit, 2 for more than one visit). The joint probabilities in the accompanying table were estimated for these random variables.

Number of Visits (Y)

Years in School (X)

1 2 3 4 0 0.07 0.05 0.03 0.02 1 0.13 0.11 0.17 0.15 2 0.04 0.04 0.09 0.10

a. Find the probability that a randomly chosen student has not visited a museum in the last year.

b. Find the means of the random variables X and Y.

c. Find and interpret the covariance between the random variables X and Y.