The triangular region shows the number of possible ounces of gold, x, and the number of possible ounces of silver, y, a jewelry maker can mix together to make a certain piece of jewelry. which combination of gold and silver can the jewelry maker use?
a.12 oz of gold and 20 oz of silver
b.10 oz of gold and 10 oz of silver
c.16 oz of gold and 30 oz of silver
d.25 oz of gold and 20 oz of silver