Answer:
The electricity cost of this refrigerator per month (30 days) = $7.488
Explanation:
Amount of power consumed by the refrigerator while running = 320 W
The refrigerator runs one-quarter of the time,
So, for 30 days, 30 × 24 hours, 720 hours,
The refrigerator uses 320 × 720 × (1/4) W.h = 57600 W.h = 57.6 KWh
And electricity costs, $0.13 per KWh,
That is, 1 KWh = $0.13
57.6 KWh = 57.6 × 0.13 = $7.488