I've been been brushing up on my micoreocnomics lately and I came across a question in Perloff that looked really simple, but for some reason I am struggling to answer:
Assume we are in the long run and each firm in a competitive market has a cost function $C = q^2$ and market demand is $Q = 24 - p$.
Determine the long-run equilibrium price, quantity per firm, market quantity and number of firms.
In the long run, profits are $0$, therefor firms should enter until $MC = AC$.
$MC = 2Q$ and $AC = Q$. Setting them equal to another we get:
$2Q = Q$, which implies $Q = 0$.
However this result seems incorrect to me, could someone please point me in the right direction. I feel like I am getting this weird result because my AC curve is linear whereas it is usually U shaped.