21. The article cited in Exercise 20 also gave the following values of the variables and

:

y 1 0 1 0 0 2 0 1 1 1 2 1 0 0 1 1 0 1 1 z 1 8 6 1 1 5 3 0 0 4 4 0 0 1 2 1 4 0 5 number of intersections y 5 number of culs-de-sac y 1 1 0 0 0 1 1 2 0 1 2 2 1 1 0 2 1 1 0 z 0 3 0 1 1 0 1 3 2 4 6 6 0 1 1 8 3 3 5 y 1 5 0 3 0 1 1 0 0 z 0 5 2 3 1 0 0 0 3

a. Construct a histogram for the y data. What proportion of these subdivisions had no culs-de-sac? At least one cul-de-sac?

b. Construct a histogram for the z data. What proportion of these subdivisions had at most five intersections? Fewer than five intersections?