1. The problem statement, all variables and given/known data In problems involving electromagnetism it is often convenient and informative to express answers in terms of a constant, x, which is a combination of the Coulomb constant, k, the charge of an electron, e, and H=h/(2pi), with h being Planck's constant. For instance, the lowest energy that a hydrogen atom can have is given by E=-(0.5)(x^2)m(c^2), where m is the mass of the electron and c is the speed of light. Which of the following is the correct expression for x? (HINT: Non-relativistic kinetic energy is (0.5)m(v^2), where v is the speed.) a) (k(e^2))/(Hc) b) H/(k(e^2)c) c) (k(e^2)H)/c d) (k(e^2)c)/H 2. Relevant equations E=hf E=m(c^2) E=(1/2)m(v^2) 3. The attempt at a solution I really don't know what they are asking for or what formula they are referring. Can someone help? Thanks.