Budgeting material purchases. The Mahoney Company has prepared a sales budget of $42,000$ finished units for a three$-$month period, ending March $31.$ The company has an inventory of $22,000$ units of finished goods on hand at December $31$ and has a target finished goods inventory of $24,000$ at the end of March.

It takes three litres of direct materials to make one unit of finished product. The company has an inventory of $90,000$ litres of direct materials at December $31$ and has a target ending inventory of $110,000$ litres.

Required: How many litres of direct materials should be purchased during the three months ending March $31?$