A woman bought two packs of toffees, with the same of number of toffees in each pack. She bought the first pack at 25 paise per toffee and the second pack at 3 toffees for 65 paise. She mixed them together and sold at Rs.3.50 a dozen. What is her gain percent?

• A.  \[15%\]        
• B.               \[25%\]           
• C.               \[16\frac{2}{3}%\]   
• D.               \[12%\]