Suspense Account

A company’s trial balance failed to agree, and a suspense account was opened for the difference.
Subsequent checking revealed that discounts allowed $13,000 had been credited to discounts received
account and an entry on the credit side of the cash book for the purchase of some machinery $18,000
had not been posted to the plant and machinery account.
Which two of the following journal entries would correct the errors?
Debit Credit
$ $
(1) Discounts allowed 13,000
Discounts received 13,000
(2) Discounts allowed 13,000
Discounts received 13,000
Suspense account 26,000
(3) Suspense account 26,000
Discounts allowed 13,000
Discounts received 13,000
(4) Plant and machinery 18,000
Suspense account 18,000
(5) Suspense account 18,000
Plant and machinery 18,000
A 1 and 4
B 2 and 5
C 2 and 4
D 3 and 5

The correct answer is C. And my doubt is why do we debit discount allowed as it should have been credited in (2)