Answer:
 1131.0 m^3
Explanation:
Let h1 represent the height of the top cone, and h2 the height of the bottom cone. The volume of a cone is given by the formula ...
 V = (1/3)πr^2·h
so the volumes of both cones together will be ...
 V = (1/3)πr^2·h1 + (1/3)πr^2·h2 = (1/3)πr^2·(h1 +h2)
 = (1/3)π(6 m)^2(12 m + 18 m) = 360π m^3
 ≈ 1131.0 m^3