21. The article cited in Exercise 20 also gave the following values of the variables y
number of culs-de-sac and z

number of intersections:

y 1 0 1 0 0 2 0 1 1 1 2 1 0 0 1 1 011 z 1 8 6 1 1 5 3 0 0 4 4 0 0 1 2 1404 y 1 1 0 0 0 1 1 2 0 1 2 2 1 1 0 2110 z 0 3 0 1 1 0 1 3 2 4 6 6 0 1 1 8 335 y 1 5 0 301 10 0 z 0 5 2 3 10 00 3

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

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