15. When Amy's income increased from $15,000 to $30,000, her consumption of macaroni decreased from 12 pounds to 6 pounds, and her consumption of soy-burgers increased from 3 pounds to 6 pounds. Using the midpoint method, we can conclude that:
(A) Macaroni and soy-burgers are both normal goods with income elasticities greater than \( 1/2 \).
(B) Macaroni is an inferior good and soy-burgers are normal goods; both have income elasticities greater than \( 1/2 \).
(C) Macaroni is an inferior good with an income elasticity less than \( 1/2 \) and soy-burgers are normal goods with an income elasticity greater than \( 1/2 \).
(D) Macaroni and soy-burgers are both inferior goods with income elasticities less than \( 1/2 \).