The Reaction 2 O₃→3 O₂ Has the Rate Law

The reaction 2 O₃→3 O₂ has the rate law:
Rate = k [O₃]²[O₂] ^{- 1} Calculate k , given that the rate of the reaction is 2.8×10 ^{- 4} mol/L × s for the initial concentrations [O₃]_o = 0.050 M and [O₂]_o = 0.010 M .

A) 1.1×10 ^{- 3} s ^{- 1}
B) 5.6×10 ^{- 5} s ^{- 1}
C) 5.6×10 ^{- 7} s ^{- 1}
D) 1.4×10 ^{- 3} s ^{- 1}
E) 7.0×10 ^{- 9} s ^{- 1}