Use the graph to determine the domain and range of the relation, and whether the relation is a function.
 a. Domain:  -10, -8, -6, -4, -2, 0, 2, 4, 6, 8, 10
 Range: y
 Yes, the relation is a function.
 b. Domain:  -10 ≤ x ≤ 10
 Range: y
 Yes, the relation is a function.
 c. Domain: x
 Range: y
 No, one y-value is shared by two x-values.
 d. Domain: x
 Range: y
 No, one y-value is shared by two x-values.