A solenoid having an inductance of $6.30 \mu \mathrm{H}$ is connected in series with a $1.20 \mathrm{k} \Omega$ resistor. (a) If a $14.0 \mathrm{~V}$ battery is inserted into the circuit, how long will it take for the current through the resistor to reach $80.0 \%$ of its final value? (b) What is the current through the resistor at time $t=1.0 \tau_{l} ?$