You need to calculate the height of the cone which would be OV, not VB
Using Pythagorean theorem:
OV = sqrt(37^2-12^2)
OV = 35
Now you have the height to solve everything.
This is a semi circle so volume and surface area would be 1/2 of a full cone.
A) v = 1/2 x pi x r^2 x h/3
V = 1/2 x pi x 12^2 x 35/3
V = 1/2 x pi x 144 x 35/3
V = 840pi
B) sa =1/2 x pi x r(r + sqrt(h^2+r^2))
Sa = 1/2 x pi x 12(12+ sqrt(35^2+12^2))
Sa= 923.63 round as needed.
C) volume of hemisphere with 4cm diameter:
2/3 x pi x 2^3 = 5.33pi
Divide volume of semi cone by volume of hemisphere:
840pi/5.33pi = 157.5