A liquid phase reaction, A $-->$ B$,$ is to be carried out in an isothermal, well mixed reactor with a volume of $20$L$.$ Initially there are $4$ moles of A$.$ The rate of destruction of A is second order with respect to A$.$ A is consumed in the

reactor at a rate of $0\mathrm{.}2$ mol$/$s$.$ What is the value of the rate constant k for the reaction $($include units$)$