A telegraph line can be modeled as a circuit comprised of a voltage source plus a resistor and an inductor in series. Consider a telegraph line with a resistance of R=102, and inductance is L=5 H. Assume that when sending a "dash," a voltage of 12 V is applied while the key is closed for 0.3 s (i.e., the circuit is closed for 0.3 s meaning that V(t) = 12 * At). Obtain the expression for the current i(t) passing through the solenoid.