Answer:

1st case,

Power, P1 = 60W

Number, n1 = 2

Time for use, T1 = 4 hours everyday

Energy consumed, E1 = n1 × P1 × T1

E1 = 2 × 60 × 4 = 480watt-hour = 0.48kWh

As a result, total energy consumed during 30 days = 30 × 0.48 = 14.4watt-hour

2nd case,

Power, P2 = 100W

Number, n2 = 3

Time for use T2 = 5 hours everyday

Energy consumed, E2 = n2 × P2 × T2

E2 = 3 × 100 × 5 = 1500 = 1.5kWh

As a result, the total energy consumed over 30 days = 30 × 1.5 = 45kWh

Thus we get,

overall energy consumed = 14.4 + 45 = 59.4kWh