A shirt costs ₹(a2 –ab -b2 ) , a pair of trousers cost ₹(2a2 +8ab-2b2 ) and a pair of shoes cost ₹(a2 –3ab+4b2 ) .After collecting these three items from the store, Ranjan paid ₹(2a+b )2 .What balance will Ranjan receive from the cashier ?