The question I'm having difficulty with is: Find the short run profit maximizing level of output and profit if the price of output is 30, and again...

The question I'm having difficulty with is:

Find the short run profit maximizing level of output and profit if the price of output is 30, and again if the price of output is 12.5.

Then, if there are 80 firms in the short run, and the market demand is P=-2(quantity demanded) + 1000, explain why P=60 is not the SRCE price. Find the SRCE price.

Can you explain how to find the short run maximizing level of output and the SRCE price by using the info on the graph? Thank you!