The volume of a rectangular prism is given by the multiplication of its three dimensions: if
are the width, height and length of the prism, the volume is

So, in your case, you have

To make a box and whisker plot you must first order the data:
11, 13, 16, 18, 21, 23, 24, 29
Then find the median:
19.5
Then split the data into two sections by the median:
11, 13, 16, 18 and 21, 23, 24, 29
Now find the medians of those sets
14.5 and 23.5
With this information we can conclude Option C is the correct plot
Hope this helps!