Answer
See below.
Work Step by Step
By plugging in $t=30$ into the formula: $L(30)=500(1-e^{-0.0061\cdot30})\approx83.61$
By plugging in $t=60$ into the formula: $L(60)=500(1-e^{-0.0061\cdot60})\approx153.25$
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