Each morning soriano buys coffee and donut holes for his employees and clients . each cup of coffee cost $2,50 and each cup of donut holes cost 1.75 . soriano bought 60 cups of coffee and donut holes and spent $123.75.

1) write a system of equations to model this situation

2) solve the system of equations to find the number of cups of coffee and cups of donut holes that soriano bought his employees and clients.

Researchers are conducting experiments to determine the role of alcohol in the development of depression. after the study is complete, they determine that the relative risk of developing depression is 1.55 with a 95 % ci of 1.2 -1.9. each group is then divided into nonsmokers and smokers. the relative risk for the nonsmokers is 1.12 with a 95% ci of 0.87-1.37. the relative risk for the smokers is 1.7 with a 95 % cl of 1.5-1.9. what type of bias may affect this study? a. procedure bias b. recall bias c. selection bias d. confounding e. lead-time bias