Okay, I'm trying to solve a person's expected utility given a budget constraint using the Lagrangian method on Maple. I keep getting the error 'Warning, solutions may have been lost'

Here is what I have so far. Can anyone tell me what I'm doing wrong?

Z:=(EU+λ*(Px*X+Py*Y+f))

solve({diff(Z,X)=0,diff(Z,Y)=0,diff(Z,f)=0,diff(Z,λ)=0}.{X,Y,f,λ})