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 value of where

A) 2.2 L/mol·s
B) 0.75 L/mol·s
C) 1.9 L/mol·s
D) 0.21 L/mol·s
E) none of these