ANSWER
The correct answer is A

Step-by-step explanation
We were told that Zada is paid at an hourly rate of $
per hour.
The unit rate of payment represents the slope of the straight line graph that models Zada's earnings. Thus

When she works for 4 hours she earns a total of $68 tells us that the point,
lies on the model straight line.
Using the formula for the point slope form

we obtain the equation as follows.
