The average annual income (in $Rs.$) of certain agricultural workers is $S$ and that of other workers is $T$. The number of agricultural workers is $11$ times that of other workers. Then the average annual income (in $Rs.$) of all the workers is

• A
  $\frac{S+T}{2}$
• B
  $\frac{S+11T}{2}$
• C
  $\frac{1+T}{11S}$
• D
  $\frac{11S+T}{12}$