Please help me understand how my professor plugged in the values

Problem 10: If the resistor in the circuit below is . : 13.1-14 and the value of the inductor is .:500- // , (a) what will be the time constant for the circus? (b) at what time will the current in the circuit be at 309% of its initial value? i (t ) V (t) L (a) 424 4(3.817 - 10 5 30 =(1 .) -TLE - 1 ( 70) 1-561 - 10 )6