ShopEasy Inc. is a specialty e$-$tailer that operates $87$ catalogue websites on the Internet. Larson Brown, Sales Director, feels that the style $($colour scheme, graphics, fonts, etc.$)$ of a website may affect its sales. He chooses three levels of design style $($neon$,$ old world and sophisticated$)$ and randomly assigns six catalogue websites to each design style. Larson's experimental design is a

normalized block design

partially randomized design

random block design

factorial design

completely randomized design