Final answer:
To find the equilibrium quantity, set the demand and supply equations equal to each other and solve for Q. After doing this with the given equations, the perfectly competitive equilibrium quantity for the bottled water manufacturer is found to be 9 units.
Step-by-step explanation:
To calculate the perfectly competitive equilibrium quantity for the bottled water manufacturer, we need to set the demand equation P = 40 - 2Q equal to the supply equation P = 4 + 2Q, because at equilibrium, the quantity demanded (Qd) equals the quantity supplied (Qs).
So, setting the two equations equal to each other, we have:
40 - 2Q = 4 + 2Q
Moving all terms involving Q to one side gives us:
40 - 4 = 2Q + 2Q
Simplifying, we find:
36 = 4Q
And dividing both sides by 4 gives us:
Q = 9
Therefore, the perfectly competitive equilibrium quantity is 9 units.