A 1.2 kg mass with an initial velocity of \(v_1 = a\hat{i}\), where \(a = 3.5\text{ m/s}\) collides with and sticks to a 3.2 kg mass with an initial velocity of \(v_2 = b\hat{j}\), where \(b = -1.8\text{ m/s}\). Find the final speed of the composite mass. Answer in units of m/s.