Task: Question Answering
Input (English): Problem: in a rare coin collection, all coins are either pure gold or pure silver, and there is initially one gold coin for every 3 silver coins. with the addition of 15 more gold coins to the collection, the ratio of gold coins to silver coins is 1 to 2. based on this information, how many total coins are there now in this collection ( after the acquisition ) ?
Options: a. 124, b. 135, c. 146, d. 157, e. 168
Output (English): b