The owner makes $2 in sales per customer
Note: The "Amount of sales" label of the question is phrased poorly. s could be better labeled "profit from sales" or at least "Amount made from sales", etc.
Step-by-step explanation:
If you logically think about how the answer (now that you know it) relates to the question, it should make simple sense.
i.e. if you consider the first column where $24 is made from 12 customers, and divide the $24 made by the 12 customers, you'll see that each customer spends $2.
Get the equation in the form y = ax2 + bx + c.
Calculate -b / 2a. This is the x-coordinate of the vertex.
To find the y-coordinate of the vertex, simply plug the value of -b / 2a into the equation for x and solve for y. This is the y-coordinate of the vertex..