The market equilibrium quantity without the $1.50 excise tax is units. The market equilibrium quantity with the $1.50 excise tax is units. The change in equilibrium quantity due to the $1.50 excise tax is units. (Note: Red colored supply curve should be Qs with no tax and Green supply curve is Qs with tax. Error below in labeling)

Equilibrium quantity without excise tax is 130 units.

Equilibrium quantity with excise tax is 110 units.

The change in equilibrium quantity is 20 units decrease due to excise tax.

Explanation:

The quantity demanded without tax is 130 units because this is equilibrium point where quantity supplied equals to quantity demanded. The quantity demanded with tax is 110 units because the price will increase by $1.50 due to excise tax. The new price would be $4.50 after excise tax so the quantity will be declined to 110 units.

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