A firm is able to obtain quantity discount on its order of material as follows:

Price per tonne

Tonne

Rs. 6.00

Less than 250

Rs. 5.90

more than 250 and less than 800

Rs. 5.80

more than 800 and less than 2,000

Rs. 5.70

more than 2,000 and less than 4,000

Rs. 5.60

4,000 and over

The annual demand for the material is 4,000 tonne. Stock holding costs are 20% of material cost per annum. The delivery cost per order is Rs. 6. You are required to calculate the best quantity to order.