The inclusion/exclusion principle states that

That is, the union has as many members as the sum of the number of members of the individual sets, minus the number of elements contained in both sets (to avoid double-counting).
Therefore,

will have the most elements when the sets

and

are disjoint, i.e.

, which would mean the most we can can in this case would be

(Note that

denotes the cardinality of the set

.)
For volume of a prism, the general rule is multiply the area of the base by the area of the height. For example, for a triangular prism, the volume would be (1/2)b*h*a if you set a = height of the prism and h = height of the triangle from the formula (1/2)bh, which is the area of a triangle.
Answer:
b) 2/6
Step-by-step explanation:
0, 1/6, 2/6, 3/6, 4/6, 5/6, 1
Hope this helps!