One mole of $A_{(g)}$ is heated to $200^{\circ} C$ in a one litre closed flask,until the following equilibrium is reached:
$A_{(g)} \rightleftharpoons B_{(g)}$
The rate of forward reaction at equilibrium is $0.02 \ mol \ L^{-1} \ min^{-1}$. What is the rate (in $mol \ L^{-1} \ min^{-1}$) of the backward reaction at equilibrium?

• A
  $0.04$
• B
  $0.01$
• C
  $0.02$
• D
  $1$