1. The problem statement, all variables and given/known data derive from the Lagrange function and with the use of the midpoint rule, the Schrodinger equation for a particle with charge e coupled to a vector potential? 2. Relevant equations L=(1/2)m Xt2+ e Xt . A(Xt,t) I mean by X== X dot, but A is a fun. of X and t 3. The attempt at a solution I even cant start such a quastion, coz this is my first course in quantum but since Im from Denemark my Pakistani teacher always gives me too much hard quastions to solve!!