A study is being conducted on the effect of gas price on the number of miles driven in a given month. Residents in two cities, one on the east coast and one on the west coast are randomly selected and asked to complete a questionnaire on the type of car they drive, the number of miles they live from work, the number of children under 18 in their household, their monthly income and the number of miles they have driven over the past 30 days. List the response variable(s).