control account

1)You are given the following information:
Receivables at 1 January 20X3 $10,000
Receivables at 31 December 20X3 $9,000
Total receipts during 20X3 (including cash sales of $5,000) $85,000
What is the figure for sales on credit during 20X3?
Answer is C $79,000, my question is. What does total receipts mean in receivables account when it comes to debits and credits?

2)The following control account has been prepared by a trainee accountant:
RECEIVABLES LEDGER CONTROL ACCOUNT
Opening balance $308,600 Cash received from credit customers $147,200
Credit sales $154,200 Discounts allowed to credit customers $1,400
Cash sales $88,100
Contras against credit balance in Payables ledger $4,600
Payables ledger 4,600 interest charged on overdue accounts $2,400
Irrecoverable debts written off 4,900
Allowance for receivables $2,800
Closing balance $396,800
What should the closing balance be when all the errors made in preparing the receivables ledger control account have been corrected?
Answer is $307,100. Why wasn’t the $2800 allowance not included in the calculation?

Yet in OPENTUTION chapter 16 example 1, you included irrecoverable debt written off of $460.