irrecoverable debt and allowance

Question:
“Panther owns her own business selling Gladiator dolls to department stores. At 30 June 20X2 she had the following balances in her books:

Trade receivables $31,450
Allowance for receivables (General) (as at 1 July 20X1) $(450)

A balance of $1,000 due from Selfrodges Co is considered irrecoverable and is to be written off. Horrids Co was in financial difficulty and Panther wished to allow for 60% of their balance of $800. She also decided to make a general allowance of 10% on her remaining trade receivables. What was the allowance for receivables in her statement of financial position at 30 June 20X2?”

My Answer

“General allowance =10%*((Trade receivables – irrevocable debts) – Horrids) = 10%*((31.45 – 1) – 0.8) = 2.965

opening allowance-450
closing allowance-2965
equal to increase in allowance-2515

irrecoverable debt-1000
increase in allowance-2515
equal -3515
really confused?
need explanation

Answers of the book:
“General allowance =10%*((Trade receivables – irrevocable debts) – Horrids) = 10%*((31.45 – 1) – 0.8) = 2.965

Specific allowance = 0.8 * 60% = 0.48
Total allowance = 3.445”