The Manufacturer of Beanie Baby Dolls Used Quarterly Price Data $P _ { t } = a + b t + c _ { 1 } D 1 _ { t } + c _ { 2 } D 2 _ { t } + c _ { 3 } D 3 _ { t }$

The manufacturer of Beanie Baby dolls used quarterly price data for 2012I - 2020IV (t = 1,...,36) and the regression equation $P _ { t } = a + b t + c _ { 1 } D 1 _ { t } + c _ { 2 } D 2 _ { t } + c _ { 3 } D 3 _ { t }$ to forecast doll prices in the year 2021. $P _ { t }$ is the quarterly price of dolls,and $D 1 _ { t } , D 2 _ { t }$ and $D 3 _ { t }$ are dummy variables for quarters I,II,and III,respectively. What is the estimated intercept of the trend line in the 4th quarter?

A) 22.8
B) 16
C) 18
D) 20
E) none of the above