Answer:
The volume of the stairway is
720 cubic inches
Explanation:
we know that
The volume of the stairway is equal to the volume of two rectangular prism
The volume of the rectangular prism is equal to

Find the volume of the larger rectangular prism
we have



substitute

Find the volume of the smaller rectangular prism
we have



substitute

Find the volume of the stairway
Adds the two volumes
