Can you please help me with the self test.

Brief illustration 21F.1 The current density The exchange current density of a Pt(s)|H2(g)|H+(aq) electrode at 298 K is 0.79 mA cm-2. Therefore, the current density when the overpotential is +5.0 mV is obtained by using eqn 21F.4 and f=F/RT=1/(25.69 mV): (0.79mAcm-2)x(5.0 mV) j=jofn= -=0.15mA cm-2 25.69 m V The current through an electrode of total area 5.0 cm2 is there- fore 0.75 mA. Self-test 217.1 What would be the current at pH=2.0, the other conditions being the same? Answer: -18 mA (cathodic)