pls help me to solve these two multiple questions

thx a lot!

Ritter Company has a balance of $80,000 in Accounts Receivable and a $4,000 credit balance in Allowance for Doubtful Accounts. If a specific customer's account with a balance of $500 is written off as uncollectable, the net realizable value of the accounts receivable will be; $76,000 $79,500 $76,500 $75,500 Th net book value of an amortizable (depreciated) asset is defined as the asset's cost less accumulated amortization cost O replacement cost O current market value