How to get the maximum and minimum Y points of OxyPlot YAxis ?

I have created an oxyplot chart in an Xamarin.Forms app, where I want to get the top Y tick value and the bottom one which are actually visible on the YAxis not the absolute ones.
In the screen shot below you see that 80 is displayed in the YAxis, I want to get the top tick and the bottom one.

The following is the code used to create the left liner axis.

weightLeftLinearAxis = new LinearAxis(){ Position = AxisPosition.Left,AxislineThickness = 17, StartPosition = 0, EndPosition = 1, IsAxisVisible = true };