m=70
((70-m)^2+(100-m)^2+(60-m)^2+(80-m)^2+(40-m)^2)/5=400

m=80
((60-m)^2+(65-m)^2+(65-m)^2+(70-m)^2+(80-m)^2+(80-m)^2
+(85-m)^2+(95-m)^2+(100-m)^2+(100-m)^2)/10=200