The number of people contacted at each level of a phone tree can be represented by f(x) = 3x, where x represents the level. what is x when f(x) = 27?
a. x = 9; at level 9, 27 people will be contacted.
b. x = 2; at level 2, 27 people will be contacted.
c. x = 24; at level 24, 27 people will be contacted.
d. x = 3; at level 3, 27 people will be contacted.