When the Shaffers had a monthly income of $8,000, they would usually eat out eight times a month. Now that the couple makes $8,500 a month, they eat out 10 times a month.

a. Compute the couple's income elasticity of demand. Explain your answer. (Is a restaurant meal a normal or an inferior good to the couple?)

b. List and explain the determinants of the price elasticity of demand.