Answer:
The size of an electric current that must flow is 999.18 Ampere.
Explanation:
Moles of electrons passed, n = 870. mmol= 0.870 mol
1 mmol = 0.001 mol
Number of electrons =
Total charge on N electrons = Q = 
Duration of time in which N electrons were passed = T = 84. seconds
Amount of current passes = I



I = 999.18 Ampere
The size of an electric current that must flow is 999.18 Ampere.