Channel Electrodes and ECE Processes

The reduction of m-iodonitrobenzene in acetonitrile solution at a platinum channel electrode is thought to follow an ECE mechanism [L. Nei et al. Electroanalysis 8 (1996) 214]  

By constructing a suitable working curve, find a value for the rate constant (s ) for the loss of iodide from the radical anion of m-iodonitrobenzene. You may assume a value for the mean diffusion coefficient, D, of 2.1 x 10 cm  

---