$1.$

Period

Actual demand

Forecast demand

Error

Absolute value

$1$

$800$

$1100$

$-300$

$300$

$300$

$2$

$1100$

$900$

$200$

$200$

$200$

$3$

$1400$

$1200$

$200$

$200$

$200$

$$

The Mean Absolute Percentage Error $($MAPE$)$ is approximately

a$.20\%$

b$.21\mathrm{.}21\%$

c$.24\mathrm{.}95\%$

d$.27\mathrm{.}50\%$