Diego bought some raisins and walnuts to make trail mix. Raisins cost $4 a pound and walnuts cost $8 a pound Diego spent $15 on both ingredients. Decide if each pair of values could be a combination of raisins and walnuts that Diego bought

• 4 pounds of raisins and 2 pounds of walnuts

• 1 pound of raisins and 1.5 pounds of walnuts

• 2.25 pounds of raisins and 0.75 pounds of walnuts

• 3.5 pounds of raisins and 1 pound of walnuts