Let’s draw the table, for better understanding.
$\begin{array} {llll} & \textbf{Anil} & \textbf{Bimal} & \textbf{Charu} \\ \text{Time:} & 60\;\text{days} & 84\;\text{days} & \\ \text{Total work:} & \text{LCM(60,84)} & = & 420\;\text{units} \\ \text{Efficiency:} & 7\;\text{units/day} & 5\;\text{units/day} & C\;\text{units/day}\end{array}$
Now, $ \underbrace{10 \times 7}_{\text{Anil 10 days work}} + \underbrace{14 \times 7}_{\text{Anil 14 days work}} + \underbrace{14 \times 5}_{\text{Bimal 14 days work }} + \underbrace{14C}_{\text{Charu 14 days work}} = 420 $
$ \Rightarrow 70 + 98 + 70 + 14c = 420 $
$ \Rightarrow 14c = 420 – 238 $
$ \Rightarrow \boxed{ 14c = 182 \; \text{units}}$
$\therefore$ The share of Charu $ = \frac{182}{420} \times 21000 = ₹ \; 9100.$
Correct Answer $: \text{B}$