The following table gives the QR company data for seven $(7)$ years; from $2015$ to $2021.$

Actual

YEAR Sales

$2015,25$

$2016,30$

$2017,27$

$2018,26$

$2019,29$

$2020,35$

$2021,31$

From the information given in company's QR table, the forecast from $2018$ to $2021$ using a $3-$period Weighted Moving Average forecasting method

with weights $1,2,3$ is:

a$.27\mathrm{.}33$;$27\mathrm{.}67$;$27\mathrm{.}33$;$30$

b$.27\mathrm{.}33$;$27\mathrm{.}67$;$26$;$25$

c$.27\mathrm{.}67$;$27$;$27\mathrm{.}67$;$31\mathrm{.}50$

d$.27\mathrm{.}33$;$27\mathrm{.}67$;$30$;$31$