2. It takes two hours to make a unit of A and three hours to make a unit of B. The number of units of B must not be more than twice the number of units of A. If up to 36 hours are available to make
A and B, find the permissible combinations of numbers of units of A and B.

...

The third and fourth box.

The major difference is that a histogram is only used to plot the frequency of score occurrences in a continuous data set that has been divided into classes, called bins.  bar charts, on the other hand, can be used for a great deal of other types ofvariables  including  ordinal  andnominal  data sets.