the answer:
the general formula of the relativistic momentum is given by p, such that
p= gamma x mo x V,
where: v= the speed of a the moving material point.(proton in our case)
mo=the initial mass of the proton=1.673 × 10–27 kg
and
gamma = 1 / sqrt(1- V² / C²), where C is the speed of the light, it is equal to 3.10^5 km/s
so gamma= 1/ sqrt(1- V² / C²)=1/ sqrt(1- 0.96²C² / C²)=1/ sqrt(1- 0.96²)=1/ sqrt(1- 0.96²)=1/ sqrt(1- 0.92)=1/ sqrt(0.08)=3.53
therefore, p= gamma x mo x V=3.53 xmox0.96C= 3.53 x1.673 × 10–27x 0.96 x 3x10^5=1.697 x 10^-21
finally p= 1.697 x 10^-21