At C,E_(c)=(ℏ^(2))/(2m)[((pi )/(a))^(2)+((pi )/(a))^(2)]=2(pi^(2)ℏ^(2))/(2ma^(2))(E_(c))/(E_(M))=2=>E_(c)=2E_(M)//jFor 3D AdrcostE=(ℏ^(2))/(2m)[k_(x)^(2)+k_(y)^(2)+k_(2)^(2)]{:[" At corner "E_(R)=(ℏ^(2))/(2m)[((pi )/(a))^(2)+((pi )/(a) ... See the full answer