MGMAT Challenge Problem of the week

Challenge Problem of the Week
Get out your scratch paper and take a stab at the 'Challenge Problem of the Week.' Created by Manhattan GMAT's expert instructors, it mimics the most advanced quantitative problems on the GMAT, those you will see at the 700+ ability levels.
Say What You Mean
Set S consists of 5 values, not necessarily in ascending order: {4, 8, 12, 16, x}. For how many values of x does the mean of set S equal the median of set S?
(A) Zero
(B) One
(C) Two
(D) Three
(E) More than three


[Read Last Week's Answer Here]