Answer
1.6 GeV/c.
Work Step by Step
The kinetic energy is given by equation 26–5b. Find $\gamma$.
$$KE=950MeV=(\gamma-1)mc^2=(\gamma-1)(938.3MeV)$$
$$\gamma = 2.012$$
Use equation 26-2 to solve for the corresponding v of 0.8678c.
The momentum is given by equation 26–4.
$$p=\gamma mv=2.012(938.3MeV/c^2)(0.8678c)=1638MeV/c\approx 1.6GeV/c$$