let a=C(7,4),b=C(7,5),c=C(7,6),and d=C(7,7).If there are 7 points on the plane,no three of which are collinear,what represents the total number of polygons that can be firmed with at least 5 sides?
a.a+b b.c+d c.a+b+c d.b+c+d
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