By Teppei Kasai TOKYO (Reuters) – Shares in Rakuten Inc fell to their lowest in over two months on Monday as investors questioned the ability of Japans biggest e-commerce firm to digest another acquisition after the company said it was considering buying a U.S. In a statement on Saturday, Rakuten said it was in talks with U.S. Japanese media said any deal would be worth at least 100 billion yen ($950 million), or almost the same amount Rakuten paid for U.S. San Francisco-based Ebates, which operates websites offering rebates and coupons from retailers like Amazon.com Inc and Best Buy Co Inc, could not be reached for comment.