First use the data in the question:
V = πr2h
8600 = πr2h
h = 8600/πr2
SO using this value for h, substitute it into the formula for surface area:
S = 2πr2 + 2πrh
S = 2πr2 + 2πr x 8600/πr2
S = 2πr2 + 17200/r
or
S = 2πr2 + 17200r-1
Hope this helps a bit...