A. The equilibrium price = $20
The equilibrium quantity = 4
b. The equilibrium price = $12
The equilibrium quantity = 2
At equilibrium
The quantity demanded = Quantity supplied
![QXd = 14-(1)/(2) Px\\\\QXs = (1)/(4) Px-1\\\\QXd =QXs\\\\](https://img.qammunity.org/2021/formulas/business/college/c4tk3ycrz0hfrrflawy5kpb3z20e31quvl.png)
Qxd = 14-0.5Px
QXs = 0.25Px-1
14-0.5Px = 0.25Px-1
Collect like terms
14+1 = 0.25Px+0.5Px
15 = 0.75Px
Px = 15/0.75
= 20
The equilibrium Quantity
= 14-0.5Px
= 14-0.5*20
= 14-10
= 4
B. With a 12 dollar excise duty
QXd =
![14-[(1)/(2) (Px+12)]](https://img.qammunity.org/2021/formulas/business/college/sga4719deqe6jnj4mjf9jmcja7kw4gnohe.png)
= 14-0.5Px-6
QXd = QXs
14-0.5Px-6 = 0.25Px-1
14-6+1 = 0.75Px
Divide through by 0.75
9/0.75 = Px
12 = Px
The equilibrium quantity
= 14-0.5Px-6
= 14-0.5*12-6
= 2
The equilibrium price is $12 and the quantity = 2
3.