find the electric flux passing through the sides if the electric field is

a) E=(-3x)i + (2y)j + (4z)k

b) E=(sin(pi*x/A)i + cos(pi*y/2A)j

for a) since the area of each side is A

^{2}, flux=A

^{2}*E, since the cube is at the origin, anything on -x,-y,-z will have o value (for x,y,z) and therfore 0 E and so 0 flux

flux=

flux from

right= 2*A*A

^{2}=2A

^{3}

left= 2*0*A

^{2}=0

top= 4*A*A

^{2}= 4A

^{3}

bottom= 4*0*A

^{2}=0

front= -3*A*A

^{2}=-3A

^{3}

back= -3*A*A

^{2}=0

for b) i cant see how they got the answers, the answers are all 0 other than ffor the left which they say is

left=-A

^{2}

but as far as i can tell, the left flux is [cos(pi*y/2A)j * A

^{2}] cos(pi/2)=0 so i dont see how they come to this??

hope i am doing this right, really not sure, any help appreciated