13.4 no 4

I'm trying to answer 13.4 #4 but its saying its wrong.

Int (dQ/dx-dP/dy) dA

Qx=4
Py=0

Int (4) * dA = 4A(Area of paralellogram) which is Area*Base

x0=6, y0=6, therefore A = 6*6 =36

=4*36 = 144

Is there anything I'm doing
wrong?

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Your contour is clockwise, instead of counter clockwise, i.e. the opposite of the direction that Green's theorem is about.  The result is that true answer is -144.