A man ordered 10 physics book and some chemistry book.The price of chemistry book is twice the price of a physics book.While preparing the bill,the cleark interchanged the number of physics and chemistry book by mistake,which decreased the bill by $$12\frac{1}{2}$$%.The ratio of the number of physics book to the number of chemistry in the original order is:

A

3:5

B

3:4

C

4:5

D

2:3