Blocks A and B are initially at rest, in contact with each other, on a horizontal frictionless surface. Block A has a mass \(m_A = 4.0 \text{ kg}\) and Block B has a mass \(m_B = 2.0 \text{ kg}\). A mechanical plunger applies a horizontal force \(F_P\) to Block A, pushing both blocks to the right. The magnitude of \(F_P\) as a function of time \(t\) is shown in the graph. The plunger loses contact with Block A at \(t = 1.0 \text{ s}\).