Need help with calculating gpa

[TommehTGOD]

need help with this program that is telling me to calculate gpa
This is the test data and output
http://tinypic.com/r/1zccyue/5

this is what i have so far..
http://tinypic.com/r/w0mk9/5

i know some things might be wrong, but i'm trying to fix it
here's the problems i'm having:
1.)How to read all the values from the input file (using sentinel values I think) even though you have some values that are skipped (or not there)
ex.)if you look at the test data you see #ID 19364 only has 4 values for that line
this is what i had put in the input file (its probably wrong, i put the -1's in the place of where some of the lines don't have all values)

http://tinypic.com/r/ndwkcw/5

2.)How do i write the code to multiply the grade and crhrs because you see that there's a grade and crhrs for each course? then i have to add up all the credit hours on each person's ID..
ex.) how will i write points =.....
Thanks

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cmath>
#include <stdlib.h>
using namespace std;

//function prototypes go here
int main()
{
	double gpa, points, hours, ID, grade, crhrs;

	ofstream OutputFile;
	OutputFile.open("Output.dat");

	ifstream infile;
	infile.open("Input.dat");

	OutputFile<<setw(30)<<"Thomas Powe"<<endl;
	OutputFile<<setw(29)<<"03-27-12"<<endl<<endl;
	OutputFile<<setw(15)<<"ID"<<setw(18)<<"GPA"<<endl<<endl;
	infile>>ID>>grade>>crhrs>>grade>>crhrs>>grade>>crhrs>>grade>>crhrs>>grade>>crhrs;
while (!infile.eof())
	{
	//OutputFile<<setw(15)<<ID<<setw(18)<<"Comin Soon"<<endl;
	points = (grade * crhrs) + (grade * crhrs) + (grade * crhrs) + (grade * crhrs) + (grade * crhrs);
	hours=crhrs + crhrs + crhrs +crhrs +crhrs;
	gpa=points/hours;
	infile>>ID>>grade>>crhrs>>grade>>crhrs>>grade>>crhrs>>grade>>crhrs>>grade>>crhrs;
	OutputFile<<setw(15)<<ID<<setw(18)<<gpa<<endl;
	}
	OutputFile.close();
	infile.close();
	return 0;
}

this what i have so far