      der(1) = exp( zlog(t-1,1)* b(2,je) + 

     $                            thetalog(t,1) * b(3,je)) 

      der(2) = b(1,je)* der(1) * zlog(t-1,1)

      der(3) = b(1,je)* der(1) * thetalog(t,1)

      