The surface area of a cone is found by
SA =π r^2 +π rl where r is the radius and l is the slant height
We know the diameter is 16 so we can find the radius by dividing the diameter in half
r = d/2 = 16/2 = 8
We know the slant height is 17.9
SA = π ( 8) ^2 + π ( 8) 17.9
= 64 π + 143.2π
=207.2π mi^2