A $12\mathrm{.}0-$V battery is connected into a series circuit containing a $14\mathrm{.}0-$ resistor and a $2\mathrm{.}30-$H inductor.

$($a$)$ In what time interval will the current reach $50\mathrm{.}0\%$ of its final value?

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$($b$)$ In what time interval will the current reach $90\mathrm{.}0\%$ of its final value?

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