You have a choice between five restaurants that differ from each other with respect to their food quality [as measured by the number of stars (*) the restaurant received in customer reviews; this ranges from one to five stars, with five being the best] as well as their price.

Which of these restaurants are on the efficient frontier?

Restaurant Quality Price 1 *** $30 2 3 4 LO 5 ** ***** *** * $25 $50 $20 $5