In a game of physics and skill, a rigid block (A) with mass m sits at rest at the edge of a frictionless air table, 1.30 m above the floor. You slide an identical block (B) with initial speed vB toward A. The blocks have a head-on elastic collision, and block A leaves the table with a horizontal velocity. The goal of the game is to have block A land on a target on the floor. The target is a horizontal distance of 1.80 m from the edge of the table.

What is the initial speed vB that accomplishes this? Neglect air resistance.