Table schema:
CREATE TABLE scientists (SSN VARCHAR, name VARCHAR); CREATE TABLE projects (hours INTEGER, code VARCHAR); CREATE TABLE assignedto (project VARCHAR, scientist VARCHAR)

Question: Find the total hours of the projects that scientists named Michael Rogers or Carol Smith are assigned to.
SQL: 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'