type BankAccount(initialSold : float, Owner : string)  = 
    let TransactHistory : string [] = null
    member val Sold = initialSold with get, set
    member this.Owner = Owner
    member this.DoTransaction(t : TransactionType) =
         let transaction = Transaction(this, t)
 
    override this.ToString() = 
        this.Owner + " has " + this.Sold.ToString() + " $."
 
type TransactionType =
| Deposit of float
| Withdraw of float
| Transfer of BankAccount * float
 
type Transaction(hostAccount : BankAccount, transactionType) =
    do match transactionType with
        | Deposit amount -> hostAccount.Sold <- hostAccount.Sold + amount
        | Withdraw amount -> hostAccount.Sold <- hostAccount.Sold - amount
        | Transfer (target, amount) -> hostAccount.Sold <- hostAccount.Sold - amount; target.Sold <- target.Sold + amount

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