College sophomore Martin enjoys attending sporting events and going to concerts. Because his scholarship pays for room and board, he spends all his income on these live events. Every once in a while, a doting aunt sends a cash gift to Martin; of course, he spends this additional sum on attending more sporting events and concerts. 

a. True or false: Both sporting events and concerts are luxury goods for Martin.

b. True or false: If concerts are a luxury good to Martin, sporting events must be an inferior good. Explain your answer, referring to the formula for the income elasticity of demand.