How to define a field variable correctly?

Hello there,

I was trying to define three field variable where angle of internal friction and cohesion depend on those field variable. But I am getting the following errors:

 ***ERROR: Internal error in look-up table generation.  Check that dateline.
         entries are sufficient to describe the dependence in all independent variables.

I am attaching the screenshot where you may see how I define the field variable. Can you please tell me the correct way to define the properties to avoid this error?