CRActivity and Contract Relations

Hi Acumatica Community;

decimal actualRevenueAmount = PXSelectGroupBy<PMProjectRevenueTotal,
     Where<PMProjectRevenueTotal.projectID, Equal<Current<Contract.contractID>>>,
     Aggregate<Sum<PMProjectRevenueTotal.curyAmount>>>
     .Select(Base)
     .RowCast<PMProjectRevenueTotal>()
     .Sum(rb => rb.CuryAmount ?? 0);

I’m developing a code. I need to connect CRActivity and Contact Dacs. There was not direct Relationship between those two. I need to get CRActivity.PercentCompletion Like above code. Can anyone help me.