A mass spectrum for an alloy made of copper and gold is displayed. Which expression can be used to find the relative atomic mass, $A_r$, of the copper in this sample?
- A$\frac{(56.36 \times 63) + (25.14 \times 65)}{56.36 + 25.14 + 18.50}$
- B$\frac{(56.36 \times 63) + (25.14 \times 65) + (18.50 \times 197)}{56.36 + 25.14 + 18.50}$
- C$\frac{(56.36 \times 63) + (25.14 \times 65)}{56.36 + 25.14}$
- D$\frac{(56.36 \times 63) + (25.14 \times 65)}{63 + 65}$