Calculate the speed of the proton after acceleration.

$\gamma  = \frac{{1855}}{{938}} = 1.977$ or $\gamma  - 1 = \frac{{917}}{{938}}$;

$\frac{v}{c} = \sqrt {1 - \frac{1}{{{\gamma ^2}}}}  = 0.86{\rm{c}}$ or $v = \frac{{1600}}{{938 \times 1.997}}{\rm{c = 0.86c}}$;

Award [2] for a bald correct answer.
Watch for ECF from (a).

in (b) gamma was often obtained correctly to find V - but many more got lost. Surprisingly no useful 'Pythagorean triangles' were seen which make understanding this topic much easier.