Economists who study production of goods by a firm consider two functions. The revenue function $R(x)$ is the revenue the firm receives when x number of units are sold. The cost function $C(x)$ is the cost the firm incurs when producing x number of units. The derivatives of these functions $R'(x)$ and $C'(x)$ are called by economists the marginal revenue and cost function. The figure shows graphs of the marginal revenue function $R'$ and the marginal cost function $C'$ for a manufacturer. Assume that $R$ and $C$ are measured in thousands of dollars.

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(a) What does the shaded area in the figure represent?

A. The increase in cost as the production level increases from 50 to 100 units.
B. The total profit that the manufacturer earns.
C. The increase in profit as the production level increases from 50 to 100 units.
D. The total revenue generated by the manufacturer.
E. The total cost generated by the manufacturer.
F. The increase in revenue as the production level increases from 50 to 100 units.

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(b) Upon closer inspection of the graph, a table of data values for $R'$ and $C'$ (each in thousands of dollars per unit manufactured) is generated below: $$\begin{array}{|c|c|c|}\hline x & R' & C' \\ \hline 50 & 2.50 & 0.84 \\ \hline 55 & 2.40 & 0.85 \\ \hline 60 & 2.30 & 0.87 \\ \hline 65 & 2.20 & 0.90 \\ \hline 70 & 2.10 & 0.95 \\ \hline 75 & 2.00 & 1.01 \\ \hline 80 & 1.90 & 1.08 \\ \hline 85 & 1.80 & 1.16 \\ \hline 90 & 1.70 & 1.24 \\ \hline 95 & 1.60 & 1.32 \\ \hline 100 & 1.50 & 1.40 \\ \hline \end{array}$$

Use the Midpoint Rule with $n = 5$ to estimate the value of the shaded region (in thousands of dollars).

Value of the shaded region = thousand dollars