Zero-momentum frame - total momentum in this frame

[Cantique]

Homework Statement

Assume that all particles are non-relativistic, that the target X is initially at rest,
and that x has kinetic energy T_x in the laboratory frame. Show that the total kinetic
energy of the reactants in the centre-of-mass frame is given by T_* = μT_x/m_x, where m_x is
the mass of particle x and μ the reduced mass of x and X. Also obtain an expression for
p_* in terms of T_* and μ.

Homework Equations

I have completed the first part of this question without a problem. The second part, requiring p_* to be found doesn't make sense to me. Surely the total momentum in the zero-momentum frame should be zero? Or is it expecting a different quantity?

The Attempt at a Solution

First part done. Second part - don't know what it is asking.

 

[dauto]

I agree. The problem isn't clear. One possible interpretation is that p* is the momentum of the incoming particle - as opposed to total momentum - as seen in the center of mass ref. frame.