In this item, it is not given that there has to be specific arrangement or order as to how the questions are going to be answered. Hence, the concept that can be used in order to answer this item is the concept of combination which states that, nCr = n! / (r!)(n - r)!
This is read as "combination of n taken r". In this item, n = 10 and r = 4. Substituting the known vaues to the equation, 10C4 = (10!) / (4!)(10 - 4)! 10C4 = 210
Therefore, the number of which is which the questions can be answered is 210.
The extra amount that Mary would pay for apples under a monopoly instead of perfect competition is B. $3
<h3>Calculations and Parameters:</h3>
From the complete information,
There are images of the prices that can be gotten under a monopoly and the ones that can be gotten in a perfect competition by Mary.
The marginal cost which is graphed against the pound of apples and the price shows Mary would pay $15 and the marginal revenue shows that Mary would pay $12.
Hence, the difference between them, which is the extra amount to be paid would be $15-$12