"The chart could use some changes, as the individual park data is hard to read because of the scale of the total data. Update the combo chart area as follows:

a$.$ Apply the Monochromatic Palette $4$ color scheme to the chart.

b$.$ Add a secondary axis for the Total series. $[$Mac Hint: Select the Total series and use the format pane to add the axis.$]$

c$.$ Add axis titles to the chart, with Spending per park as the left vertical axis title, and Total spending as the right vertical axis title. Delete the horizontal axis title placeholder."