A.Cách 1: \(E = \left\{ {79;\,\,80;\,\,81;\,\,82;\,\,83;\,\,84;\,\,85} \right\}\)
B.Cách 1: \(E = \left\{ {80;\,\,81;\,\,82;\,\,83;\,\,84;\,\,85} \right\}\)
C.Cách 1: \(E = \left\{ {79;\,\,80;\,\,81;\,\,82;\,\,83;\,\,84} \right\}\)
D.Cách 1: \(E = \left\{ {79;\,\,80;\,\,81;\,\,82;\,\,83;\,\,84;\,\,85} \right\}\)