Which of the following results would lead the auditor to suspect that the doubtful debt provision is likely to be understated?

Revenue for the company in the last quarter of the accounting period is usually thirty per cent higher than in the first three quarters.

The current doubtful debt provision is three per cent of the total receivables balance at the period end, compared to five per cent in the previous three years.

The positive receivables confirmation resulted in fifty per cent of the respondents confirming their outstanding balance at the period end with the client company.

The company has recently revised its credit terms from 60 days to 45 days.