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

Please teach me this question. Thank you very much.