Acell phone store sells the basic model of a phone for $30 and the upgraded model for $100 when a customer signs a two-year agreement. on tuesday, the store has $900 in sales. the store pays $5 for each basic model and $25 for each upgraded model. if the cost of the cell phones sold on tuesday is $200, how many upgraded models were sold?

Stu and ambrose are working together on a study of whether diet is related to students' mental health. first, they randomly select 10 students from the student center and 10 students from the office of counseling and psychological services. then, they ask students to rate their diet in terms of healthiness on a scale of 1-100 before completing a 20-item mental health survey. a) name one of the constructs being studied b) how was the construct you named above operationally defined in this experiment? e) was the variable you described above their independent variable, their dependent variable, or a controlled variable? d) what is a confounding variable? what is a potential confound in this study?