Thread: using the C++ sort stl

I'm tasked with building a program that sorts a list of employees by name and by salary using the sort stl in the c++ library. Theres a code at this site: STL Sort Comparison Function - CodeProject (see section "Function Pointer as a Comparison object")
that I've been playing around with, (it sorts a person by age ive modified it to sort by name and age), but I would like to place the boolean functions inside of the Person class instead of outside it and make the age and name variables private. However, I get an error in my main file inside "std::sort", regarding my functions "sortName" and "sortAge" and with my private variables and I'm not sure how to fix it.

sort header

Code:

class Person
{
public:
    // default constructor
    Person();
        
        //constructor for age and name empty
    Person(int a,string n) {
       
            age = a;
               name = n;
       
               
    };
        
        
 
     
bool sortAge(Person a, Person b);


bool sortName(Person a, Person b);




private:
    int age;
    string name;

sort.cpp

Code:

//sorts the age
bool Person::sortAge(Person a, Person b)
{
    
    return a.age < b.age;
}
//sorts the name
bool Person::sortName(Person a, Person b){
   
    return a.name < b.name;
    
}

       int main()
{
    
 
    vector<Person> vecPerson;
       vecPerson.push_back(Person(22,"Calvin"));
      vecPerson.push_back(Person(20,"James"));
    vecPerson.push_back(Person(30,"Benny"));
    vecPerson.push_back(Person(28,"Alison"));
         vecPerson.push_back(Person(35,"Major"));
        vecPerson.push_back(Person(39,"Mark"));
     
                //sorted by name
        cout << "******Sorted by Names*****\n";        
    std::sort(vecPerson.begin(), vecPerson.end(),sortName);
         
        for(size_t i=0; i<vecPerson.size(); ++i)
        std::cout<<vecPerson[i].name<<", "<<vecPerson[i].age<<std::endl;

            //sorts by number
     cout << "*****Names Sorted by Age*****\n";   
   std::sort(vecPerson.begin(),vecPerson.end(),sortAge);

    for(size_t i=0; i<vecPerson.size(); ++i)
        std::cout<<vecPerson[i].age<<", "<<vecPerson[i].name<<std::endl;
      
    
    return 0;
}