7.2.2. The number of cars waiting to be served at a gas station was counted
at the beginning of every minute during the morning rush hour. The frequency
distribution is given below. Determine the relative frequency distribution
associated with these data and draw the histogram.

Number of Cars  |   Number of occurences
----------------------------------------
       0        |          0
       1        |          9
       2        |         21
       3        |         15
       4        |         12
       5        |          3



--------------



7.2.6. An urn contains three red balls and four white balls. A sample of
3 balls is selected at random and the number of red balls observed. Determine
the probability distribution of this experiment and draw its histogram.