Ошибка в учебнике или я чего то не понимаю

#ifndef EMPLOYEE_H_
#define EMPLOYEE_H_
 
class Employee{
public:
    Employee(const char*,const char*);
    virtual ~Employee();
    const char* getFirstName()const;
    const char* getLastName()const;
    virtual double earnings()const=0;//чистая виртуальная функция
    virtual void print()const;//виртуальная функция
private:
    char* firstName;
    char* lastName;
};
#endif /* EMPLOYEE_H_ */

#include "Employee.h"
#include <cstring>
#include <cassert>
#include <iostream>
using std::cout;
 
Employee::Employee(const char* first,const char* last){
    firstName=new char[strlen(first)+1];
    assert(firstName!=0);
    strcpy(firstName,first);
 
    lastName=new char[strlen(last)+1];
    assert(lastName!=0);
    strcpy(lastName,last);
}
Employee::~Employee(){
    delete [] firstName;
    delete [] lastName;
}
const char* Employee::getFirstName()const{
    return firstName;
}
const char* Employee::getLastName()const{
    return lastName;
}
void Employee::print()const{
    cout<<firstName<<" "<<lastName;
}

#ifndef BOSS_H_
#define BOSS_H_
#include "Employee.h"
class Boss:Employee{
public:
    Boss(const char*, const char*, double);
    virtual ~Boss();
    void SetWeeklySalary(double);
    virtual double earanings()const;
    virtual void print()const;
private:
    double weeklySalary;
};
#endif /* BOSS_H_ */

#include "Boss.h"
#include <iostream>
using std::cout;
Boss::Boss(const char* first,const char* last, double s):Employee(first,last){
    SetWeeklySalary(s);
}
Boss::~Boss(){}
void Boss::SetWeeklySalary(double s){
    weeklySalary=(s>0?s:0);
}
double Boss::earanings()const{
    return weeklySalary;
}
void Boss::print()const{
    cout<<"Администратор:  ";
    Employee::print();
}

#ifndef COMMISSIONWORKER_H_
#define COMMISSIONWORKER_H_
#include "Employee.h"
class CommissionWorker:Employee{
public:
    CommissionWorker(const char*, const char*, double=0.0,double=0.0,int=0);
    virtual ~CommissionWorker();
    void setSalary(double);
    void setCommission(double);
    void setQuantity(int);
    virtual double earnings()const;
    virtual void print()const;
private:
    double salary;//базовая зп за неделю
    double commission;//комиссионная зп
    int quantity;//количество проданных деталей
};
#endif /* COMMISSIONWORKER_H_ */

#include <iostream>
#include "CommissionWorker.h"
using std::cout;
 
CommissionWorker::CommissionWorker(const char* first, const char* last,double s,double c,int q)
:Employee(first,last){
    setSalary(s);
    setCommission(c);
    setQuantity(q);
}
CommissionWorker::~CommissionWorker(){}
void CommissionWorker::setSalary(double s){
    salary=s>0?s:0;
}
void CommissionWorker::setCommission(double c){
    commission=c>0?c:0;
}
void CommissionWorker::setQuantity(int q){
    quantity=q>0?q:0;
}
double CommissionWorker::earnings()const{
    return (salary+commission*quantity);
}
void CommissionWorker::print()const{
    cout<<"Работник на коммиссионных";
    Employee::print();
}

#include <iostream>
#include "Employee.h"
#include "Boss.h"
#include "CommissionWorker.h"
using namespace std;
 
int main() {
    Boss b("Макс","Казаков", 10000.99);
    b.print();
    cout << "Заработал " <<b.earanings()<< endl; // prints !!!Hello World!!!
    return 0;
}