in this rxn A--2B+C, the rate const of rxn is 2x10^-3 molL^-1s^-1.if initial conc of A is 1.6 mol L^-1 then what would b conc of A and B after 10min respectively?

The rate of reaction for the above equation can be written as:
$Rate = -\frac{\Delta \left[A\right] }{\Delta t}=\frac{1}{2}\frac{\Delta \left[B\right] }{\Delta t} =\frac{\Delta \left[C\right] }{\Delta t}$ ....(i)

Units of rate constant = mol/ (L s)
Which means the mentioned reaction is an example of zero order reaction, we known for zero order reaction, the rate = rate constant 
Therefore 
Rate = 2 $\times$ 10^-3 mol L^-1 s^-1 
For A, the initial concentration is 1.6 mol L^-1
Initial time = 0s 
And final time = 600 s
Substitute the value in equation 1, we get 

$$\begin{gathered} 2 \times {10}^{-3} =- \frac{( A_f- 1.6)}{600 s} \\ 1.2 = -A_f + 1.6 \\ {A}_f = 1.6 - 1.2 \\ {A}_f = 0.4 M \\ Similary for B, \\ 2 \times {10}^{-3} =\frac{1}{2}\frac{( Bf- 0)}{600 s} \\ 2.4 M = B_f \end{gathered}$$
Hence, amount of B formed after 10 min = 2.4 M 
Whereas amount of A left after 10 min = 0.4 M