Two Isomers (A and B)of a Given Compound Dimerize as Follows

Two isomers (A and B) of a given compound dimerize as follows:

Both processes are known to be second order in reactant,and k₁ is known to be 0.25 L/mol·s at 25°C,where

In a particular experiment,A and B were placed in separate containers at 25°,where [A]₀ = 1.0 $\times$ 10^-2 M and [B]₀ = 2.5 $\times$ 10^-2 M.It was found that [A] = 3[B] after the reactions progressed for 3.0 minutes.
-Calculate the concentration of A₂ after 3.0 minutes.

A) 2.8 $\times$ 10^-22 M
B) 6.9 $\times$ 10^-3 M
C) 3.1 $\times$ 10^-3 M
D) 1.6 $\times$ 10^-3 M
E) none of these