Tickets for high demand events are often resold on a secondary market, such as StubHub or VividSeats. Suppose a consumer is interested in determining if there is a significant difference in ticket prices between the two resale sites. She picks an upcoming event being held at a large venue and randomly selects 15 seating areas in the venue. She then records the resale ticket prices for each area from the two sites. Which test(s) can be used for each situation below? 

a. The distribution of the differences in prices suggests the population of price differences is approximately Normal.

b. The differences in price follow a right-skewed distribution.

Choose from the following tests, as appropriate: paired t-test, sign test, two-sample t test, and Mann-Whitney test. There may be two acceptable choices.