please answer this question carefully

John really enjoys eating Nathan's hot dogs in New York City. His marginal utilities from the first three hot dogs he consumes are 200, 150, and 125, respectively. His total utility when he consumes three hot dogs is: O a. 475 b. 350 Oc 200 O d. 125 Alexandra notices that the marginal utility of working with a tutor seems to fail with each hour the tutor helps her study. If Alexandra keups the tutor untia her grade actually begins to fall, her marginal utility for the last hour of tutoring will be Da negativo Ob. 0. c. immeasurable. Od positive, but rising more slowly