12/7 = 20/x
12x = 140
x = 140/12 = 35/3 = 11.67
so radius of the large cone = 11.67 ft
Volume = 1/3 πr^2h
= 1/3(3.14)(11.67)^2(20)
= 2850.88
Answer is B. 2850.70 ft^3
