There are four candles which can burn for 5 hours, 4 hours, 3 hours and 2 hours respectively

There are four candles which can burn for 5 hours, 4 hours, 3 hours and 2 hours respectively. All of them are lighted at the same time. They are kept lighted till the time 3 candles are finished. If the cost of lighting each candle is Rs. 1.50 per hour, what will be the total expenditure?
(a) Rs.16.50
(b) Rs.18.00
(c) Rs.19.50
(d) 21.00