OK, it’s official: The price of Amazon Prime, which offers unlimited two-day shipping and other perks for $79, is increasing to $99 per year. Amazon’s stock was up over 2 percent on Thursday morning. If you’re an Amazon Prime member now and your membership was set to renew before April 17, 2014, you’ll still pay $79 for that renewal. Prime memberships renewing after April 17 will be $99. And new Prime members will pay $99 per year starting March 20. (So if you’ve been thinking about signing up for Prime, do it now and save $20.) In addition to unlimited two-day shipping, Prime offers instant video and lets Kindle owners borrow one ebook every month (from a library of largely self-published titles). Amazon is also reportedly working on a streaming music service for Prime members.