The marked price of a book is 20% more than the cost price. After the book is sold, the vendor realizes that the he had wrongly raised the cost price by a margin of 25%. If the marked price of the book is Rs. 30, what is the original cost price of the book?
1
Rs. 25
2
Rs. 20
3
Rs. 45
4
Rs. 30
5
None of these