Sally has an income of $1000 a month and buys 8 pizzas every month. When Sally has a raise and a new income of $1800 a month, she buys 4 pizzas every month.

A. Calculate the income elasticity of demand for Sally's consumption of pizzas. You must show ALL of your work for this question (general formula, partial work and so on). Express your answer to two decimal places.

B. What is the proper terminology for this type of good?