Seven Hundred Gallons of 91-Octane Gasoline Is Obtained by Mixing $$\left\{ \begin{array} { c } x + y = 85 \\87 x + 94 y = 63,700\end{array} \right.$$

Multiple Choice

Seven hundred gallons of 91-octane gasoline is obtained by mixing 87-octane gasoline with 94-octane gasoline.Write a system of equations in which one equation represents the amount of final mixture required and the other represents the amounts of 87- and 94-octane gasolines in the final mixture.Let x and y represent the numbers of gallons of 87-octane and 94-octane gasolines,respectively. ​

A) ​ $$\left\{ \begin{array} { c } x + y = 85 \\87 x + 94 y = 63,700\end{array} \right.$$
B) ​ $$\left\{ \begin{array} { c } 87 x + 94 y = 700 \\x + y = 85\end{array} \right.$$
C) ​ $$\left\{ \begin{array} { l } x + y = 63,700 \\87 x + 94 y = 85\end{array} \right.$$
D) ​ $$\left\{ \begin{array} { c } 87 x + 94 y = 700 \\x + y = 63,700\end{array} \right.$$
E) ​ $$\left\{ \begin{array} { c } x + y = 700 \\87 x + 94 y = 63,700\end{array} \right.$$