An Individual Derives Utility from Consuming "All Other Goods," G,and

Multiple Choice

An individual derives utility from consuming "all other goods," g,and clean air (measured by the reduction in particulate matter per m³) ,a,as measured by the utility function U(g,a) = g^0.6a^0.4.The price of consumer goods equals $20 and the price of clean air (abatement) equals $10.What is the slope of the Engel curve when income increases from $100 to $200?

A) The slope is 25.
B) The slope is -25.
C) The slope is zero.
D) The slope is infinite.