ΔMBN= ΔCBA
MB/CB= BN/BA= MN/CA
6/BC= 4/BA= 5/10
5BC= 4*10
5BC= 60
BC= 60/5
BC=12
CN= BC-BN= 12-4=8
5AB= 4*10
5AB= 40
AB= 40/5
AB=8
