Answer:
The cost of one unit of electricity is $0.185
Step-by-step explanation:
Amount charged = $120.99
Units of electricity used = 654
The cost of a unit of electricity can be determined by dividing the amount charged by the number of units used.
So that,
cost of one unit of electricity = 
= 0.185
cost of one unit of electricity = $0.185
This implies that the cost of electricity used is charged at $0.185 per unit.
Thus for 654 units of electricity used, the cost would be;
654 x $0.185 = $120.99