B.D = Face value - Amount received = 1800 - 1782 = Rs 18
i = 5 % = 0.05
Now, the bill was drawn on 10th September 2010 for 6 months, so legally due date is 13th March 2011. But the bill was encashed 73 days before 13th March 2011.
Counting 73 days backwards, 13 days of March + 28 days of February + 31 days of January + 1 day of December 2010 = 73 days.
The bill was encashed on 31 – 1 i.e, 30th December 2010