What is the sum of hours for projects that scientists with the name Michael Rogers or Carol Smith are assigned to?
SELECT sum(T2.hours) FROM assignedto AS T1 JOIN projects AS T2 ON T1.project  =  T2.code JOIN scientists AS T3 ON T1.scientist  =  T3.SSN WHERE T3.name  =  'Michael Rogers' OR T3.name  =  'Carol Smith'
SELECT sum(T2.hours) FROM assignedto AS T1 JOIN projects AS T2 ON T1.project  =  T2.code JOIN scientists AS T3 ON T1.scientist  =  T3.SSN WHERE T3.name  =  'Michael Rogers' OR T3.name  =  'Carol Smith'
[{'sum(T2.hours)': 6702}]