What are the concentrations

What are the concentrations

The following reaction was monitored as a function of time:
AB –> A + B
A plot of 1/[AB] versus time yields a straight line with slope 5.9×10^?2 (M*s^-1).
So: k=5.9×10^-2
and
Rate= k[AB]^2 (so it is a second-order reaction)

If the initial concentration of [AB] is 0.260 M, and the reaction mixtur…