Which relations represent a function?

a.
(16, 14)
(14, −12 )
(9, 11)
(10, 14)

b.
(10, 8)
(7, 9 )
(9, 13)
(8, 5)

c.
(18, 24)
(16, 10 )
(5, 13)
(18, 14)

d.
(14, 12)
(10, 12 )
(−13, 7)
(11, 15)

Studies show that massage therapy has a variety of health benefits and it is not too expensive. a sample of 12 typical one-hour massage therapy sessions showed an average charge of $58. the population standard deviation for a one-hour session is =$5.55. a. what assumptions about the population should we be willing to make if a margin of error is desired? (select your the population has uniform distribution/ the population is at least approximately normal is required/ the population has no exponential distribution/ no assumptions should be made) b. using 90% confidence, what is the margin of error (to 2 decimals) c. using 99% confidence, what is the margin of error (to 2 decimals)