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' <table_name> : Scientists col : SSN | Name row 1 : 123234877 | Michael Rogers row 2 : 152934485 | Anand Manikutty row 3 : 222364883 | Carol Smith row 4 : 326587417 | Joe Stevens row 5 : 332154719 | Mary-Anne Foster row 6 : 332569843 | George ODonnell row 7 : 546523478 | John Doe row 8 : 631231482 | David Smith row 9 : 654873219 | Zacary Efron row 10 : 745685214 | Eric Goldsmith row 11 : 845657245 | Elizabeth Doe row 12 : 845657246 | Kumar Swamy <table_name> : Projects col : Code | Name | Hours row 1 : AeH1 | Winds: Studying Bernoullis Principle | 156 row 2 : AeH2 | Aerodynamics and Bridge Design | 189 row 3 : AeH3 | Aerodynamics and Gas Mileage | 256 row 4 : AeH4 | Aerodynamics and Ice Hockey | 789 row 5 : AeH5 | Aerodynamics of a Football | 98 row 6 : AeH6 | Aerodynamics of Air Hockey | 89 row 7 : Ast1 | A Matter of Time | 112 row 8 : Ast2 | A Puzzling Parallax | 299 row 9 : Ast3 | Build Your Own Telescope | 6546 row 10 : Bte1 | Juicy: Extracting Apple Juice with Pectinase | 321 row 11 : Bte2 | A Magnetic Primer Designer | 9684 row 12 : Bte3 | Bacterial Transformation Efficiency | 321 row 13 : Che1 | A Silver-Cleaning Battery | 545 row 14 : Che2 | A Soluble Separation Solution | 778 <table_name> : AssignedTo col : Scientist | Project row 1 : 123234877 | AeH1 row 2 : 152934485 | AeH3 row 3 : 222364883 | Ast3 row 4 : 326587417 | Ast3 row 5 : 332154719 | Bte1 row 6 : 546523478 | Che1 row 7 : 631231482 | Ast3 row 8 : 654873219 | Che1 row 9 : 745685214 | AeH3 row 10 : 845657245 | Ast1 row 11 : 845657246 | Ast2 row 12 : 332569843 | AeH4
col : sum(T2.hours) row 1 : 6702