Answer:
I haven't answered a question like this in a while but I'll just give it a shot:
I think it's 816.4
Explanation:
h=13
20/2=10 so I believe that 10 would be the r (radius)
So then the equation could be:
S= 2(3.14)10Ă—13
Multiply them all together and you get 816.4^^