Problem Solving

A \(\$200\) investment at \(x\) percent per annum and a \(\$500\) investment at \(y\) percent per annum have a combined yearly return of \(10\) percent of the total of the two investments. If \(\$400\) is invested at \(x\) percent and \(\$600\) is invested at \(y\) percent per annum to give a combined yearly return of \(9.2\) percent of the total of the two investments, what will be the combined percentage yearly return of the total investment if \(\$100\) each is invested at \(x\) percent per annum and \(y\) percent per annum respectively?

A. \(5\%\)
B. \(7.5\%\)
C. \(8.5\%\)
D. \(10\%\)
E. \(17\%\)

Answer: C

Source: e-GMAT