Data for price and thickness of soap is entered into a statistics software package and results in a regression equation of = 0.4 + 0.2x.

What is the correct interpretation of the slope if the price is the response variable and the thickness is an explanatory variable?

• The price of the soap increases by $0.40, on average, when the thickness increases by 1 cm.
• The price of the soap decreases by $0.40, on average, when the thickness increases by 1 cm.
• The price of the soap increases by $0.20, on average, when the thickness increases by 1 cm.
• The price of the soap decreases by $0.20, on average, when the thickness increases by 1 cm.