Solution
φ
s1
=−E
y
l
2
=−Cl
2
,
φ
s2
=E
z
l
2
=−DL
2
,
φ
s3
=E
y
l
2
=CL
2
,
φ
s4
=−E
z
l
2
=DL
2
,
φ
s5
=E
x
l
2
=−BL
2
,
φ
s6
=−E
x
l
2
=BL
2