[twinnie]

I have tried to program a grade program but it keeps not printing out correctly
Please help

#include <stdio.h>  //standard library header file

int
 main( void)
{
	int grade;
	printf("Enter score number ");
	scanf("%i", &grade);
	if (grade < 0 || grade > 100)
	{
		printf("not valid");
	} 
	else if  (grade <= 0 && grade>= 59)
	{
		printf("F");
	 }
	else if (grade <= 60 && grade>= 69)
	{
		printf("D");
	}
	 else if  (grade >= 79 && grade<= 70)
	 {
		printf("C");
	 }
	  else if (grade <= 80 && grade>= 89)
	 {
		printf("B");
	 }
	else if (grade <= 90 && grade>= 100)
	{
		printf("A");
	 }
	  return 0;
}