Trail Balance, Income statement and suspense account

Trying to prepare an Income statement and balance sheet.

The trial balance shows that there is a suspense account for £18,000 (on the credit side)

My question is:

On further investigation of the suspense account it was discovered that a cash receipt of £18,000 had been posted to the suspense account. This represents the proceeds from the disposal of a piece of equipment that had been bought exactly two and half years ago at a cost of £22,000. The equipment was sold on the last day of the financial year.

How do i work this out?
Many thanks