In the drawing below, the two red dots are where the red 27 yd altitude of
the entire figure intersects the top and bottom of the prism base on which
the pyramid sits.  I have split the 27 yd altitude into 9 yd at the bottom
and 18 yd. at the top. 



We break the figure into two parts:

This prism with a right triangle base:



The area of the right triangle bottom (and top) 
is found by 

yd².

The volume of this prism is

yd³.

and sitting on top of that prism is this pyramid:


 
The volume of this pyramid is

yd³.

We add the two volumes together:

Total volume = 650yd³ + 780yd³ = 1430yd³

Edwin