Using the following data, perform exponential smoothing to forecast day $21$ demand? How about if you need to forecast day $21,22$ and $23$ demands?

day demand

$165$

$271$

$353$

$468$

$577$

$679$

$744$

$855$

$964$

$1063$

$1165$

$1265$

$1368$

$1451$

$1551$

$1661$

$1757$

$1873$

$1963$