Given a reference text about Lotus Mark IX, who designed the car?

Context: The Lotus Mark IX was an aluminium-bodied sports racing car manufactured by Lotus Engineering Ltd. About thirty of the Mark IX sports racing cars were made. It was closely related to the Lotus model Mark VIII, of which only about seven cars were made. These cars were largely based on the innovative space frame of the Lotus Mark VI. The highly aerodynamic bodies were designed by Frank Costin and constructed by Williams & Pritchard Limited.

During this early era, of 1954–1955, Lotus Engineering was still a fledgling company, and cars were delivered in different states of completion on special orders. Similar to the Mark VIII, the Mark IX was available in various configurations and different engines, including the 1500 cc MG, 1500 cc Connaught and 2-litre Bristol were fitted. However, the Mark IX designation is most often powered by the 1100 cc Coventry Climax engine. Apparently, two models of Mark IX were offered – the "Club" and the "Le Mans", the latter of which had larger drum brakes fitted.

Answer: The Lotus Mark IX was designed by Frank Costin.