Without knowing exactly what 
is, this is impossible to do. So let's assume 
. Then the line integral over the given rectangle will correspond to the "signed" perimeter of the region.
You don't specify that the loop is complete, so in fact the integral will only give the "signed" length of three sides.
Parameterize the region by first partitioning the contour into three sub-contours:
where
for each sub-contour. Then the line integral is given by
with
. You have
Then the integral over the entire contour would be
. Note that if the loop is complete, then the last leg of the contour would evaluate to -5, and so the total would end up as 0. This result would also follow from the fact that 
is conservative, i.e. 
for some scalar field 
, and so the line integral is path independent. Its value would depend only on the endpoints of the contour, which in the case of a closed loop would simply be 0.
You don't specify that the loop is complete, so in fact the integral will only give the "signed" length of three sides.
Parameterize the region by first partitioning the contour into three sub-contours:
where
with
Then the integral over the entire contour would be