Answer
0.9 MeV/revolution.
Work Step by Step
We assume that the speed of the protons is c. Calculate the period T, the time for one revolution.
$$T=\frac{2\pi r}{c}$$
The number of revolutions N is the total time t divided by the period.
$$N=\frac{t}{T}=\frac{ct}{2 \pi r}$$
The energy per revolution is the total energy gained divided by the number of revolutions.
$$=\frac{\Delta E}{N}=\frac{(\Delta E) 2 \pi r }{ct}$$
$$=\frac{(1.0\times10^{12}eV-150\times10^{9}eV) 2 \pi (1000m) }{(3.00\times10^8 m/s)(20 s)}$$
$$=0.9 MeV/rev$$
