Hi, I've attached the problem and the solution. I understand the solution except for one thing. I've circled the part I'm having problems with. How do I decide if the circled part should be f2(x,y,z)=x2-y2-z or f2(x,y,z)=z-x2+y2 I'm sure it has something to do with the fact that the problem statement states that the bee is moving in the increasing direction of z, but I just can't figure out how it translates into f2 being one or the other. Or are both answers acceptable? Thanks in advance for the help!