An amount of $Rs. 5000$ is put into three investments at the rate of interest of $6\%,7\%$ and $8\%$ per annum respectively . The total annual income is $Rs. 385$ If the combined income from the first two investments is $Rs. 70$ more than the income from the third , find the amount of each investment by matrix method.

Question

$\begin{array}{1 1} 1000,2000,1800 \\ 30,40,50 \\ 1000,2200,1800 \\ 70,80,90\end{array}$