Calculate Australian Tax in C

tax.c

#include <stdio.h>
/* Australian Tax Rates verified with https://www.ato.gov.au/Calculators-and-tools/Host/?anchor=STC&anchor=STC#STC/questions  */

int myearnings(void);

int main()
{
int unsigned long earnings,tax1,tax2,tax0;
int unsigned deftax[] = {0,3572,19822};

for (;;)
   {	
	printf("How much do you earn?\n");
	earnings=myearnings();

	tax0 = (earnings-18201)*.19+deftax[0];
	tax1 = (earnings-37001)*.325+deftax[1];
	tax2 = (earnings-87000)*.37+deftax[2];

	if(earnings<18200) {
		printf("Try again, earnings less than 18200\n");
		scanf("%lu",&earnings);
		if(earnings<18200)	
		    printf("Sorry exiting program, run again if you want to recalculate");
		    break;
    }
        else if(earnings<=37000)
                printf("You will get taxed $%d.\nSo for the year you will earn $%d\n",tax0,earnings-tax0);

        else if(earnings<=87000)
    {
		printf("\nYou will get taxed $%d.\nSo for the year you will earn $%d\n",tax1,earnings-tax1);
		printf("That means that you will earn $%d fortnightly or $%d weekly\n",(earnings-tax1)/26,(earnings-tax1)/52);
    }
        else if(earnings>87000)
    {            
		printf("You will get taxed $%d.\nSo for the year you will earn $%d\n",tax2,earnings-tax2);
    }    

	printf("\npress \"cntrl c\" to exit, or enter another amount!\n\n");

   }

	return(0);

} /* Main */

int myearnings(void)
{
	long unsigned int a;
	scanf("%d",&a);
	return(a);
}