Ali extracted the trial balance of his business as at $30$ June $2020$ and the totals of the debit and credit columns agree. However, Ali did not realise that there are certain kinds of errors that would not affect the agreement of the trial balance. As Ali's good friend, you helped him to identify the following errors:

a$.$ A sale of RM$60$ worth of goods to Abu Bakar has been completely omitted from the books.

b$.$ A sale of goods for RM$4,125$ to A$.$ Rajeswary had been entered in error into A$.$ Rakeswary's account.

c$.$ The purchase of machinery for RM$2,000$ had been debited to purchases account. Machinery is bought and used as a non$-$current asset.

d$.$ In the cash book, the amount of cash sales transferred to the sales account was understated by RM$40$ and the amount transferred to the salaries account was also understated by RM$40.$

e$.$ A sale of goods to Fatima was entered in the books as RM$280.$ The correct amount as stated in the invoice was RM$288.$

f$.$ A payment of cash of RM$32$ to AB Bookshops was entered on the receipts side of the cash book in error and credited to AB Bookshop's account.

g$.$ A credit purchase from Mae costing RM$89$ was entered in the books as RM$98.$

Required:

Identify the types of error that Ali had made for items $($a$)$ to $($g$)$ above.