SELECT sum(Spent) FROM Student JOIN Visits_Restaurant ON Student.StuID = Visits_Restaurant.StuID WHERE Student.Fname = "Linda" AND Student.Lname = "Smith";
How long does student Linda Smith spend on the restaurant in total?
[Schema (values) (types)]: | restaurant_1 |  Student : stuid (text) , lname (number) , fname (text) , age (text) , sex (number) , major (text) , advisor (number) , city_code (number) | Restaurant : resid (text) , resname (number) , address (text) , rating (text) | Type_Of_Restaurant : resid (text) , restypeid (number) | Restaurant_Type : restypeid (text) , restypename (number) , restypedescription (text) | Visits_Restaurant : stuid (text) , resid (number) , time (text) , spent (text);