To find the surface area of the cone, we use the following formula
S = pi x r x h + pi x r²
Where 'S' represents the surface area, 'r' the radius of the base, and 'h' the slant height.
from your question, we get the following information:
r = 14/2 = 7
h = 20
S = Surface area(the thing we're trying to calculate)
If you just plug those informations into the equation, we get the following
S = 3.14 x 7 x 20 + 3.14 x 7² = 3.14 x 140 + 3.14 x 49 = 593.46 cm²
Then, we get this final answer. The surface area of this cone is 593.46 cm²