28. (a)
R
S
Theta
Phi
E
F
.5
.5
0
0
0
0
.5
.5
0
0
.5
0
.333
.333
0
0
0
.667
(b)
R
S
Theta
Phi
E
F
.5
.5
0
0
0
0
.5
.5
0
0
.5
0
.5
.5
90
90
1
.5
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