Solve the Problem $\$ 980, \$ 950, \$ 1200$ And $\$ 520$

Multiple Choice

Solve the problem.
-During the first four months of the year, Jack earned $\$ 980, \$ 950, \$ 1200$ and $\$ 520$ . If Jack must have an average salary of at least $\$ 850$ in order to earn retirement benefits, what must Jack earn in the fifth month in order to qualify for benefits?

A) at most $\$ 913$
B) at least $\$ 600$
C) at least $\$ 900$
D) at most $\$ 850$