Your answer is the last option, 615.44 ft³.
We know this as the formula for the volume of a cone is [(π × r²) × ]/3, and substituting in our numbers, with 3.14 being π, we get:
[(3.14 × 7²) × 12]/3 = (153.86 × 12)/3 = 1846.32/3 = 615.44
I hope this helps!