In the circuit given the switch is closed at time $t=0$ What is the amount of charge passing through the battery in are time constant ?

Question

$(a)\;\frac{eR^2E}{L} \\ (b)\;E \bigg(\frac{L}{R}\bigg) \\(c)\;\frac{EL}{eR^2} \\(d)\;\frac{eL}{ER}$