Use the following to answer questions a-e: A 20l2 study investigated the impact of psychological stress on men's judgements of their own happiness. The men were randomly assigned to one of two groups; one group was assigned to participate in a stressful task while the other group did not take part in the task. Then the men were asked to rate the their happiness from very sad to very happy. a. What are the cases in this study? ( 2 pt) b. Briey explain why this is an experiment and not an observational study. (2 pt) 0. Identify the explanatory variable in this experirrlbit. (1 pt) d. Identify the response variable in this experiment.( 1 pt)