Which relation is a function? Select all that apply {(5,1), (4,1), (3, 1), (2,1)}

{(5,3). (4,1), (3, 2), (2,0)}

{(5,2), (2,5), (5. 3), (3,5)}

{(5,5). (4,4), (3, 3), (2,2}

{(5,1), (5,2), (5, 3), (5.4)}

Your friend uses c=50p to find the total cost, c, for the people, p, entering a local amusement park is the cost of admission proportional to the amount of people entering the amusement park? explain.