This is the question I wanna ask
The question 2 in http://www.math.harvard.edu/archive/21a_spring_09/PDF/13-07-Stokes-thm.pdf is similar to the question I asked, but I still have no idea how to do the question.
For (i) I tried to convert the equation into $r(t)$ format.
The vector field $(F) = (y,z,x)$ from the question
Let's say $C1$ is the line from $(3,0,0)$ to $(0,4,0)$
so $r(t)=(3-3t, 4t, 0)$
$r'(t)= (-3,4,0)dt$
then after integrating $C1,C2$ and $C3,$ I added them together, the answer is $-23.5.$
In (ii), I got $-18$
there must be something wrong because i and ii should give the same answer.