You can always post 2 seperate posts.
I'm going to try the second problem.
There are equations to use to find the volume/surface area of the frustum.
https://www.cuemath.com/measurement/volume-of-frustum/
https://www.varsitytutors.com/hotmath/hotmath_help/topics/surface-area-of-a-cone
Try to imagine the frustum as a complete cone, with the base being 12 radius and a line cutting it at 9 radius. The height would be from 12 radius to the tip (0 radius). For the height to increase by 4 the radius subtracted by 3. (12/3)*4 = 16, the height of the whole cone is 16.
To find the volume, we're looking for the big cone (radius of 12) subtracted by the little cone (radius of 9). The volume of the big cone is 12^2*pi*16/3 = 768pi.
The volume of the small cone is 9^2*pi*(16-4)/3 = 324pi.
768pi - 324pi = 444pi.
To find the surface area, we're going to start by focusing on the lateral surface.
The lateral surface of the big cone (radius of 12) is sqrt(16^2+12^2)*12*pi = 240pi.
The lateral surface of the little cone (raduis of 12) is sqrt(9^2+12^2)*9*pi = 135pi.
The lateral surface of the frustum is 240pi - 135pi = 105pi.
Next the bases. pi*9^2 + pi*12^2 = 225pi.
225pi + 105pi = 330pi.
330pi + 444pi = 774pi.
Sorry if the explanation is the bit confusing, please ask questions if you don't understand anything.
=^._.^=