Ok so, the condition that causes firms to enter the market is when firms are making Super Normal Profit. This is when Average Total cost curve is under the MR=D=AR=P line. So firms outside the market are attracted to the SNP being made, and the profits get competed out until normal profit is being made. That’s when ATC is equal to MR=D=AR=P line. If more people enter the market, that’s when a loss is being made.
