26. Aden's Gifts is a highly competitive firm which can sell Aden's ink pens for $5.00 each. Given the data provided in the table below. A. What will the marginal cost be for production at output level 4 (that is, when Q=4)? Show your work and explain your answer. B. Complete the table by filling in the blanks. C. At what level of output does Aden maximize profit? Show your work and state the profit maximizing rule. Q P TC TR MR MC Profit 0 $5 $9 1 $5 $10 2 $5 $12 3 $5 $15 4 $5 $19 5 $5 $24 6 $5 $30 7 $5 $45 27. In the early 1900s, the City of Chicago employed the U.S. Army Corps of Engineers to literally reverse the flow of Chicago River. Chicago was at the time the meat-packing and slaughterhouse "Capital of the World". The river used to flow east, into Lake Michigan. After reversal, the river flows south and west, where waters merge with the Desplaines River, the Mississippi River, and ultimately the Gulf of Mexico. Write a 1-2 paragraph essay explaining the following: (1) What words would an economist use to describe the fundamental problem of the polluted Chicago river? (2) What problems, if any, were solved, and what new problems were created, by the reversal? (3) Were better solutions available? Give at least one example of a more efficient (and effective) solution. Extra credit for illustrating the problem and your proposed solution on a graph or two. 27. Consider the following article from the Chicago Tribune (10/30/2018)