Amazon.com Inc. Chief Executive Officer Jeff Bezos cut prices and added features to the Kindle to defend it against a threat from Apple Inc. in the fast- growing market for electronic readers. Amazon introduced two new versions of the device today, including a $139 model that works with Wi-Fi. A second version, with 3G mobile technology as well as Wi-Fi to download books, costs $189. Bloomberg News reported details in May about Amazon’s plans for the Kindle, its bestselling product.