Answer:
Option B is correct.
Explanation:
If we take the day 4 earnings, the graph shows their 32 hours earnings.

We can see that Joanna earns $350 at day 4. So, her hourly wage is :
≈ $11.00 (approx)
And Richard earns approximately $270 for 32 hours. So, his hourly wage is:
≈ $8.50 (approx)
We can also check the average by taking day 3 wages.
Joanna earns approximately $260 in 24 hours. So, her hourly wage is :
≈ $11.00
Richard earns $200 approx in 24 hours. So, his hourly wage is :
≈ $8.50 or 8.00 (this is not option)
Hence, after calculating the approximate wages, we can see that Joanna earns approx $11.00 per hour and Richard earns approx $8.50
Therefore, option B. Joanna earns $11.00 an hour; Richard earns $8.50 an hour - is true.