Fourty Liters of a 40% Acid Solution Is Obtained by Mixing

Multiple Choice

Fourty liters of a 40% acid solution is obtained by mixing a 28% solution with a 50% solution.Write a system of equations in which one equation represents the amount of final mixture required and the other represents the percent of acid in the final mixture.Let x and y represent the amounts of the 28% and 50% solutions,respectively. ​

A) ​ $$\left\{ \begin{array} { l } x + y = 40 \\0.28 x + 0.5 y = 40\end{array} \right.$$
B) ​ $$\left\{ \begin{array} { l } 0.28 x + 0.5 y = 40 \\x + y = 16\end{array} \right.$$
C) $$\left\{ \begin{array} { l } x + y = 40 \\0.28 x + 0.5 y = 16\end{array} \right.$$
D) ​ $$\left\{ \begin{array} { l } x + y = 40 \\0.28 x + 0.5 y = 16\end{array} \right.$$
E) ​ $$\left\{ \begin{array} { l } 0.28 x + 0.5 y = 40 \\x + y = 16\end{array} \right.$$