Explanation:
the volume of a cone is
base area × height / 3
and the case area is a circle, so we get
pi×r²×h/3
with e being the radius (half of the diameter), and h being the height.
therefore
pi×(11.9/2)²×3.5/3 = pi×(5.95)²×3.5/3 = 41.30291667... ft³