a$.$ Use the simple exponential smoothing with $a=0\mathrm{.}2$ for making forecasts.

Note: Do not round intermediate calculations. Round final answers to $2$ decimal places.

b$.$ Use the in$-$sample forecast errors to compute MSE, MAD, and MAPE.

Note: Do not round intermediate calculations. Round final answers to $2$ decimal places.

c$.$ Make a forecast for period $21.$

Note: Do not round intermediate calculations. Round final answer to $2$ decimal places.

hat$(2)21$

data:

t yt

$163$

$272$

$368$

$468$

$560$

$665$

$767$

$863$

$963$

$1062$

$1171$

$1270$

$1372$

$1481$

$1571$

$1679$

$1781$

$1879$

$1978$

$2072$