Use the $3-$period moving average 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.

data:

t yt

$149$

$245$

$339$

$445$

$551$

$659$

$761$

$870$

$980$

$1084$

$1196$

$1296$

$1396$

$1488$

$1582$

$1684$

$1776$

$1868$

$1966$

$2065$