The volume of a pyramide is
V = Ab.h/3
In this case Ab = 7 . 7 = 49
V = 49.h/3
V = 49.11/3
V = 539/3
Now let's see the cone volume
V = π.r².h/3
V = π.3².11/3
V = π.3.11
V = 33π
Now we just remove the cone from the pyramid
539/3 - 33π = 75,994cm³
Rounding its 76cm³