Consider a particular phone that has a battery rated at 5,000 mAh. The battery operates at a potential differnce of 3.90 V. How much energy in units of Kilowatt-hours, is stored in a fully charged.

a) 19.5 kWh
b) 19.0 kWh
c) 18.5 kWh
d) 18.0 kWh