The table below represents how marco feels about chocolate candy bars.

The satisfaction level gained when a customer consumes a product is total utility.It calculated by finding the total sum of utility from consumption.

Marginal utility is the rate of change of total utility and quantity consumed.

Here you apply the expression, Marginal utility=change in total utility/change in quantity consumed

Let, Marginal utility=MU

Total utility=TU

Quantity consumed=QC

Then MU=ΔTU ÷Δ QC

Given the table

Chocolate Candy Bars          Total Utility(utils)          Marginal Utility(utils)

0                                                      0                                 -

1                                                        25                             x

2                                                         y                             17

3                                                      54                                z

4                                                     a                                  b

5                                                      66                                4

6                                                      c                                   -1

Here you have assigned the missing areas with letter, hence finding the real values of the letters;

Apply MU=ΔTU÷ΔQC

Answers

y=42,x=25,z=12,a=62,b=8,c=65

Replace the letters with the real numbers in filling the table.

8(-10x+3.5y-7)

8×-10x + 8×3.5y + 8×-7

-80x + 28y - 56

therefore

-80x+28y-56 is the correct answer