Nokia’s Lumia 900 will make its U.S. launch on April 8, at which point AT&T will begin selling the phone for a relatively modest $99. The handset isn’t the first Windows Phone-powered Nokia device to hit the U.S. market — T-Mobile has carried the Lumia 710 for months. However, the LTE-enabled Lumia 900 is a more powerful and feature-filled model that rivals existing flagship phones in many respects.