Question

When an 80.0 liter vessel containing 2.00 mole of NO2(g) was heatedto 200oC, 6% of the NO2(g) decomposed to NO(g) and O2(g). What isKc for the reaction at this temperature?

2NO2(g) <--> 2NO(g) + O2(g)

(a) 3.1 x 10-6
(b) 8.3 x 10-3
(c) 2.7 x 10-2
(d) 2.1 x 10-4
(e) 6.2.x 10-5

I've been arriving at 9.05x10^-7 as my answer for Kc for somereason. The answer is noted as A. Can anybody please help?Thanks.