Two uniform smooth spheres \(A\) and \(B\) of equal radii have masses \(m\) and \(k m\) respectively. The two spheres are moving on a horizontal surface with speeds \(u\) and \(\frac{5}{8} u\) respectively. Immediately before the spheres collide, \(A\) is travelling along the line of centres, and \(B\) 's direction of motion makes an angle \(\alpha\) with the line of centres (see diagram). The coefficient of restitution between the spheres is \(\frac{2}{3}\) and \(\tan \alpha=\frac{3}{4}\).

After the collision, the direction of motion of \(B\) is perpendicular to the line of centres.
(a) Find the value of \(k\).
(b) Find the loss in the total kinetic energy as a result of the collision.