For a polygon to be regular <u>all sides and angles</u> have to be the same! A square is an example of a regular polygon, since all sides and angles are even, a rectangle is not.
The volume would be 167.344 cubic inches because 4.25 times 3.75 times 10.5 or 10 1/2 is 167.34375 but you would round so your answer would be 167.344 cubic inches.