i have already seen in chegg i want new answer

Starbucks wants to launch its new cold-brewed coffee, but they are not sure what will be the reaction of usual customers. They decided to conduct an experiment in which 1000 Starbucks cardholder (or app holders) are randomly assigned to two groups. The first group is given free sample of the new cold-brewed coffee. Both groups are sent gift rewards to redeem at participating Starbucks stores. The Starbucks computer system showed that 240 of sent reward were redeemed by the group that tried the free samples, and 200 were redeemed by the group that did not. a. Draw the design of this field experiment diagrammatically. (5 marks) b. What are threats to internal validity of this experiment