Suppose Surface S is a unit cube that has an outward orientation.
in each part , determine whether the flux of the vector field F(x,y,z) = zj across the specified face is positive, negative, or zero.

a) the face x=1
b) the face x=0
c) the face y=1
d) the face y=0
e) the face z=1
f) the face z=0

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