Calculate the cost of switching to the new policy?

Calculate the Net Present Value (NPV) if the firm switches to the new policy?

Camping Outdoor is a small manufacturer of outdoor equipment and camping gear, who operates on a cash-only basis. The firm received a request from several clients to extend credit to "net two months (60 days)". The selling price for one of its popular tables is R2 300 per unit, the variable cost per unit is R900, the current quantity sold per month is 1 800 while the quantity sold under the new policy will increase to 2 100 per month. The required rate of return is 8% per month