Protons are injected into a linear accelerator so that they have $K=250 \mathrm{keV}$ as they coast through the first drift tube. The frequency of the AC voltage applied to the tubes is $50 \mathrm{MHz}$ and the peak potential difference across each gap is $200 \mathrm{kV}$. Consider a proton that passes from the first to the second tube properly synchronized at the peak potential drop. (a) How long must the second tube be if the proton is to arrive at the next gap in proper synchronization with the accelerating voltage? (b) How long must the tenth tube be?