A Flask Is Charged with 0

A flask is charged with 0.124 mol of A and allowed to react to form B according to the reaction A(g) -B(g) . The following data are obtained for [A] as the reaction proceeds:
-The average rate of disappearance of A between 10 s and 20 s is mol/s.

A) 1.1 × 10^{- 3}
B) 4.4 × 10^{- 3}
C) 9.90 × 10^{- 3}
D) 454
E) 2.2 × 10^{- 3}