Rolls-Royce has picked up a $200m order for Trent 700 engines to go into Tunisair's three Airbus A330 aircraft.The order, the first time the airline has selected Trent engines, also includes a long-term service agreement.Rolls-Royce says the Trent 700 is the only engine specifically designed for the Airbus A330 and over 1,000 are now in service or on firm order. It has announced $2.2bn worth of Trent 700 orders in the last four months.