In a Town of 10,000 People, the Number of People $\frac { 1 } { 10 }$

In a town of 10,000 people, the number of people who during each day first hear the news of a local tax increase is one-tenth the number of people who have not yet heard the news. If f(t) stands for the number of informed people in the town, what is the differential equation f(t) satisfies?

A) f'(t) + $\frac { 1 } { 10 }$ f(t) = 10,000
B) f(t) = $\frac { 10 f ^ { \prime } ( t ) } { 10,000 }$
C) f'(t) = $\frac { 1 } { 10 }$ (10,000 - f(t) )
D) f'(t) = $\frac { 1 } { 10 }$ f(t)
E) none of these