B$)[5$ points$]$ Calculate the total energy of a proton when its kinetic energy is exactly half of its total energy. Express your answer in J $($joules$).($You may use scientific notation with three significant figures.$)$

C$)[5$ points$]$ Calculate the speed of a proton when its kinetic energy is exactly half its rest energy. Express your answer in $\frac{m}{s}.($You may use scientific notation with three significant figures.$)$

Problem $4[15$ points$]$

An electron has a de Broglie wavelength $=5\mathrm{.}5{10}^{-10}m.$ Mass of electron is $m_e=9\mathrm{.}1{10}^{-31}kg.$ The Planck's constant is $h=6\mathrm{.}63{10}^{-34}J*s.$

A$)[5$ points$]$ What is its momentum?

B$)[5$ points$]$ What is its speed? $($Hint: You should use the classical formula for momentum: $p=mv$ although you know the relativistic formula $p=mv).$