Classes - Got 4 erros and have no idea whats wrong. Please take a look and give me some advice

#include <iostream>
#include <iomanip>
using namespace std;
const double INCREASE = 0.076;
class Salary
{
public:
	void setSal(float sal);
	float newSal();
	float getRetroactive(float num);
private:
	float newSalary;
	float oldSalary;
	float retroactive;
};



void Salary::setSal(float sal)
{
	oldSalary = sal;
}

float Salary::newSal()
{
	newSalary = oldSalary * (1 + INCREASE);
	return newSalary;
}
float Salary::getRetroactive(float num)
{
	retroactive = (num - oldSalary) / 2;
	return retroactive;
}

 
#include <iostream>
#include <iomanip>
#include "newSalary.cpp"
using namespace std;



int main()
{
	Salary ss;
	float oSal, nSal, ret, monthly, nMonthly;
	cout << "Enter current salary: ";
	cin >>oSal;
	monthly = oSal / 12;
	ss.setSal(oSal);
	nSal = ss.newSal();
	nMonthly = nSal / 12;
	ret = ss.getRetroactive(oSal);
	cout << "Old Monthly is: " << monthly << endl;
	cout << "New Monthly is: " << nMonthly << endl << endl;
	cout << "Old Salary is: " << oSal << endl;
	cout << "New Salary is: " << nSal << endl << endl;
	cout << "Retroactive is: " << ret << endl;
	
	return 0;
}

class Salary
{
public:
	void setSal(float sal);
	float newSal();
	float getRetroactive(float num);
private:
	float newSalary;
	float oldSalary;
	float retroactive;
};