// constructor initializes courseName with string supplied as argument
GradeBook::GradeBook( string name, string instname )
{
   setCourseName( name ); // call set function to initialize courseName
   setInstrutorName( instname );//exercício 3.11
} // end GradeBook constructor
// Constructor
GradeBook::GradeBook(const std::string &name, const std::string &instructor) {
    setCourseName(name);
    setInstructorName(instructor);
}