Калькулятор для вычисления семестровой оценки. Оптимизация

#include <iostream> 
using namespace std; 
int main(void) 
{
char name[15];
float AG, TG, FE;
double CW, FG, num1, num2;
cout << "The name of a Student is" << endl;
cin >> name;
//Clear the screen
system("cls");
cout << name << "`s Assigment grade is " << endl;
cin >> AG;
system("cls");
cout << name << "`s Test grade is " << endl;
cin >> TG;
system("cls");
cout << name << "`s Final exam grade is " << endl;
cin >> FE;
system("cls");
//Arithmetic calculations
num1 = AG * 20 + TG * 80;
CW = num1 / 100;
num2 = CW * 40 + FE * 60;
FG = num2 / 100;
//Statements
if (FG >= 81) {
cout << name << "`s Final grade is A" << endl;
}
else if (FG >= 71){
cout << name << "`s Final grade is B" << endl;
}
else if (FG >= 61){
cout << name << "`s Final grade is C" << endl;
}
else if (FG >= 50){
cout << name << "`s Final grade is D" << endl;
}
else {
cout << name << "`s Final grade is F" << endl;
}
system("Pause"); 
}

 //Statements
if (FG >= 81) {
mark = A;
}
else if (FG >= 71){
mark = B;
}
else if (FG >= 61){
mark = C;
}
else if (FG >= 50){
mark = D;
}
else {
mark = F;
}
cout << name << "`s Final grade is " <<  mark << endl;

char mark;
//...............
mark='A';

//Arithmetic calculations
num1 = AG * 20 + TG * 80;
CW = num1 / 100;
num2 = CW * 40 + FE * 60;
FG = num2 / 100;