Study the diagram below carefully and use the given information to answer the questions that follow:

(a) Determine: (i) the profit maximizing output; (ii) the firm's profit if it produces 600 units of output; (iii) the total cost if the firm produces 400 units. 
(b) Calculate the (I) total revenue (ii) profit of the firm at the output level of 900 units 
(c) What will happen if a firm's market price falls below its average variable cost?