#### Answer

$\Delta S = 0.001462~S$

#### Work Step by Step

$\Delta S = 0.034~S~sin~[\frac{2\pi~(82.5-N)}{365.25}]$
We can find $\Delta S$ when $N = 80$:
$\Delta S = 0.034~S~sin~[\frac{2\pi~(82.5-80)}{365.25}]$
$\Delta S = 0.034~S~sin~[\frac{5\pi}{365.25}]$
$\Delta S = 0.034~S~(0.043)$
$\Delta S = 0.001462~S$