A trial balance drawn up at the end of Jim’s financial year balanced. The following errors were then discovered:

1. Goods returned to K Weston had been debited to K Wilton.

2. Repairs to office equipment had been debited in the office equipment account.

3. An invoice, $1,000, for goods sold on credit to Jacob & Co had been recorded in the accounts as $100.

4. Goods purchased on credit from Brixton Ltd had been debited in Brixton’s account and credited in the purchases account.

a. State the type of error made in each of the errors 1–4.

b. Name two further errors not revealed by a trial balance.