Inductance, volt drop and time constant??? Help

Good evening all, I am looking for some clarity on a question I am answering at the moment.



An inductor of negligible resistance and an inductance of 0.2H is connected in series with a 330ohm resistor to a 12v d.c. Supply determine:



A - the time constant of the circuit

B - the voltage drop across the inductor after two time constants

C - the voltage drop across the inductor after three time constants

D - the resistance of a 0.2H coil used to replace the inductor if the circuits time constant falls to 0.55s



Attempt so far

I = V/R = 12/330 = 36.36mA

A - t=L/R = 0.2/330 = 606microseconds

B - I'm trying to use Ve exp -Rt/L but it does seem to be giving me any answers that make sense?!

C - same as B

D - R= L/t = 0.2/0.00055 = 363.64 ohms



Any help would be greatly appreciated.



Thanks