An 8-year-old boy is brought by his parents to the psychiatrist with a 9 months history of making careless mistakes and not listening in class or at home. His mother stated that he had an unduly high distractibility during doing his homework. He is easily forgetful and often loses his books and red scarf. He is noted to be fidgety, talking excessively and interrupting others. Which of the following medications is the most likely to help with this boy’s symptoms