The rate law for the reaction below is given by the expression $ k [A][B] \; A+B \to Product $ If the concentration of $B$ is increased from $0.1$ to $ 0.3 \;mole$, keeping the value of $A$ at $0.1 \; mole$, the rate constant will be :

Question

$\begin{array}{1 1}(1) k \\(2) k/3\\ (3) 3k\\ (4) 9k \end{array} $