Differential Equation - RC cricuit

A pacemaker consists of a switch, a battery of constant voltage E sub 0, a capacitor with constant capacitance C, and the heart as a resistor with constant resistance R. When the switch is closed the capacitor charges; when the switch is opne, the capacitor discharges, sending an electrical stimulus to the heart. During the time the heart is being stimulated the voltage E across the heart satisfies the linear differential eq

dE/dt = - 1/ (RC) * E

Solve the DE subject to E(4) = E sub 0