R语言问题求助

rainviewer

open.account=function(total){
     list(
     deposit=function(amount,total){
     if(amount==0)
     stop('Deposits must be positive!\n')
     total=total+amount
     cat(amount,"deposited. Your balance is",total,"\n\n")
     },
     withdraw=function(amount,total){
     if(amount>total)
     stop("You don't have that much money!\n")
     total=total-amount
     cat(amount,"withdraw. Your balance is",total,"\n\n")

     },
     balance=function(total){
     total=total
     cat("Your balance is",total,"\n\n")
     total}
       )
    }
跪求分析：当运行这段代码时，total参数是怎么传递的？假设如下调用
total=100
ross=open.account(total)
ross$withdraw(30)
ross$balance()##怎么使得这条命令成功运行？