Submissions to the Tri-Town Community Action Agency's Substance Abuse Prevention School Poster Contest will be on display at Stop & Shop, 11 Commerce Way (Atwood Avenue Plaza), Johnston, from March 1 through March 6. On Friday, March 5, from 3 to 7 p.m., and Saturday, March 6, from 10 a.m. to 3 p.m., representatives from the Johnston Substance Abuse Prevention Coalition will be there, encouraging customers to cast their vote. All voters will be eligible to win a $50 gift card donated by Stop and Shop. The winning poster entry will receive a $500 gift card and the design will be used on a billboard. The contest was open to middle school and high school students from Johnston, North Providence and Smithfield.