Professor Jackson is studying the effect of age on income level of Mexican immigrants to the United States. In this study, the attributes of the variable "income level" could be Group of answer choices 0-20 years, 21-40 years, 41-60 years, 61-90 years, more than 80 years $0-19,999, $20,000-39,999, $40,000-69,999, $70,000 or more Income level cannot be a variable Income level does not have attributes