Need to create an Expression for max value Y-axis in a bar chart using RangeMax

[analyticsuser]

I have a requirement to display the reference lines in a bar chart. The bars in the chart are driven by UNITS measure and the reference lines are Bench10 and Bench20, the chart doesnt display the reference lines if the values of Bench10 and 20 are greater than Units. I'm using this expression:

Below is the screenshot as well where the reference lines arent being displayed. Need help with the set expression on how to achieve this.

=If(GetSelectedCount(Name) = 1 and GetSelectedCount(DepartmentName) = 1,
RangeMax(Aggr({<Year=>} Max([Bench10],Month),
Max([Bench20], Month),
Max([Units], Month) )
),

If(GetSelectedCount(Name) = 1,
RangeMax( Max([Bench10], Month),
Max([Bench20], Month),
Max([# Units], Month)
) 
)
)

[Qrishna]

Some data please?