A new manufacturer of women's cosmetics was planning to retail the company's products through mail order. The management was considering the use of direct-mail advertisements to stimulate the sales of their products. Prior to committing themselves to advertising through direct mail, the management conducted an experiment. A random sample of 1,000 consumers was selected from Mumbai. The sample was divided into two groups, with each subject being randomly assigned to one of the two groups. Direct- mail advertisements were sent twice over a period of one month to the respondents of one of the groups. Two weeks later, the respondents of both groups were mailed the company's catalog of cosmetics. Sales to each group were monitored. a) Determine what type of design is being used? Explain. b) Diagrammatically represent the design. c) Discuss the threats to internal validity and external validity for the design.