Perfect competition questions I have problems with deciding whether those statements are true or false.


In a short/long run price of equilibrium on a perfectly compettive market might be either lower or higher then average total cost of one company operating on this market.
In a short run total amount of companies in perfectly competitive branch of industry, changes when their economic gains are equal to zero.


Appreciate your help with some further comments about that. 

PS. anticipating your questions i am preparing to an exam, that is why i am looking for an answer to those questions.
I'm not going to answer the questions for you, but here is some food for thought, you should be able to conclude yourself.

Ad 1

We know that in the long run equilibrium, there are zero profits: If they'd be positive, firms would enter, if they'd be negative, firms would leave. Can we conclude something about a firm's profits if it has average total costs smaller (larger) than the price?

Ad 2

What induces change in the total amount of companies in such a branch? Is having zero-profits one of these reasons?