E
2
Σ
0
=
(
E
1
+
E
2
)
(
E
1
+
E
2
)
∗
=
E
2
10
+
E
2
20
+
E
1
E
∗
2
+
E
∗
1
E
2
E
Σ
0
2
=
(
E
1
+
E
2
)
(
E
1
+
E
2
)
∗
=
E
10
2
+
E
20
2
+
E
1
E
2
∗
+
E
1
∗
E
2
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