Answer :
Adding balaces is not right at all
for eg if i have 1000
spent balance
100 900
100 800
100 700
100 600
100 500
500 0
Acc to this i'l have 3500 which makes no sense
for eg if i have 1000
spent balance
100 900
100 800
100 700
100 600
100 500
500 0
Acc to this i'l have 3500 which makes no sense