So it basically sum of volume of 10 trapezoid prism.
So,
area of a floor y = area of the ceiling of the floor x, where y=x+1

So, basically we can find the vloume of 10 different trapezoid prism and sum them up.

V= (1/2)*(Area of the floor  + area of its celing) * (height of the room)
V=(15/2)*(Area of the floor+Area of the celing) [Notice that height of the room is the same for each floor=15 units)
Total Volume= sum of all Vs.
for instance,
V1= (25+23)* (15) cubic units
    =360 unit^3.

So your total volume should be 2190 cubic units.