$66.$ Consider the following forecast errors. What is the Mean Absolute Deviation $($MAD$)?$

Period Error

$1-2$

$21$

$33$

$40$

$5-1$

$62$

$74$

a$.1$

b$.1\mathrm{.}86$

c$.7$

d$.13$

e$.5$

$67.$ Consider the following time series data. Suppose that you use exponential smoothing with an alpha of $0\mathrm{.}7$ to fit a forecasting model. The forecast for period $7$ is

Period Forecast Actual value

Period $11010$

Period $21011$

Period $310\mathrm{.}79$

Period $49\mathrm{.}5112$

Period $511\mathrm{.}25313$

Period $612\mathrm{.}47611$

a$.10\mathrm{.}443$

b$.12$

c$.9\mathrm{.}443$

d$.12\mathrm{.}443$

e$.11\mathrm{.}443$