Proton$-$beam therapy is a treatment in which high$-$energy protons are fired at a

tumor. Upon colliding with the tumor, the protons$$ kinetic energy is used to break

apart the tumor$$s DNA and kill its cells. Suppose a particular tumor requires $0\mathrm{.}10$ J

worth of proton kinetic energy to be sufficiently destroyed. And suppose that the

protons are accelerated from rest through a $10$ MV $($megavolt$)$ potential difference

when fired at the tumor. How many protons need to be fired at the tumor in this way

to destroy it$?$ An order$-$of$-$magnitude estimate is sufficient. $[$electric potential,

potential energy, voltage, energy conservation$]$