Answer:
The combined profit of the cartel will be $12
Explanation:
TC=FC+MC*Q ........ the MC is constant so it is equal to average variable cost
MC=$4 at all levels
TR=P*Q
MR(n)=(TR(n)-TR(p))/(n-p)
it is true for n>p
profit=TR-TC
A cartel maximize profit at MR=MC or the nearest lower MC
the output is Q=3 units and P=$10
profit=$12