Delta PDA Distributors has an investment in accounts receivable of $2,750,000. Daily credit sales are $118,280. If 30% of Delta's credit customers receive a discount by paying within 10 days and the remainder of Delta's customers pay in 40 days, what is the net period that Delta maintains?

1. 31 days.

2. 40 days.

3. 37 days.

4. 19 days.

The given answer is A. Please tell me why.

(There is a possibility for the answer to be wrong)