$10.$ For the Park Spending $2018-2021$ combo chart, update the 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, and then enter Spending per park as the left vertical axis title, and then enter Total spending as the right vertical axis title. Finally, delete the horizontal axis title placeholder.