A family uses the electrical appliances listed below. Assume a 30-day month.
(a) (i) Refrigerator: 200W, operates 24 h per day but draws power only 40\% of the time.
(b) (ii) Two ceiling fans: 75W each, 12h per day.
(c) (iii) Three incandescent lamps: 60W each, 5h per day.
(d) (iv) Washing machine: 500W, 45min per day.
(e) The supply company levies the following slab rates per month:
• First 100 units at ₹4 per unit
• Next 200 units at ₹6 per unit
• Units beyond 300 at ₹8 per unit
A fixed meter charge of ₹120 is added to every bill.
(f) (a) Calculate the total electrical energy consumed in the month (in kWh).
(g) (b) Determine the total amount payable for the month.
(h) (c) If the three incandescent lamps are replaced by three LED lamps of 10W each used for the same duration, recalculate the monthly energy consumption and bill.
(i) (d) Estimate the annual monetary saving achieved by the replacement, assuming the pattern of use remains unchanged for 12 months.