Step-by-step explanation:
the surface area (base area plus side wall) of a cone is, when we have the radius and the length of the slanted side wall :
SA = pi×r×(r + l)
in our case here
r = half of the diameter = 12/2 = 6 m
l = 13.4 m
so, we have
SA = pi×6×(6 + 13.4) = pi×6×19.4 = 365.6813849... m²
