# 5/7 Bleep Bleep Math problem

#1

var cashRegister = {
total:0,
lastTransactionAmount: 0,

``````add: function(itemCost) {
this.total +=  itemCost;
this.lastTransactionAmount = itemCost;
},
scan: function(item,quantity) {
switch (item) {
case "eggs": this.add(0.98 * quantity); break;
case "milk": this.add(1.23 * quantity); break;
case "magazine": this.add(4.99 * quantity); break;
case "chocolate": this.add(0.45 * quantity); break;
}
return true;
},
voidLastTransaction: function() {
this.total -= this.lastTransactionAmount;
}``````

};

cashRegister.scan('eggs',1);
cashRegister.scan('milk',1);
cashRegister.scan('magazine',1);
cashRegister.scan('chocolate',3);

//Show the total bill

This is my code.
When I click submit it passes.

Shouldn't it be 7.2? because as I understood the total amount should be decreased by the sum of last transaction (3x chocolate which cost 0.45 each) ;

#2

But you have not voided anything, you made the function, but did not call it out. Math is correct with the code you provided.

And at first you should have 4 chocolates, then with void you change it to 3

#3

cashRegister.voidLastTransaction();

cashRegister.scan("chocolate", 3);

#4

I understood.
thank you very much.