Calculate Electric Bill

/* Line charge = 50 tk */
/* For first 100 units, 1 unit = 5 tk */
/* For next 400 units, 1 unit = 6.5 tk */
/* For usage above 500 units, 1 unit = 8 tk */

#include <stdio.h>

int main()
{
    int unit;
    double cost = 100;

    printf("Enter the number of units used: ");
    scanf("%d", &unit);

    if(unit <= 100)
        cost = cost + unit * 5;
        else if(unit <= 500)
            cost = cost + 100*5 + (unit - 100) * 6.5;
        else
            cost = cost + 100*5 + 400*6.5 + (unit - 500) * 8;

        printf("Total cost = %lf\n", cost);

    return 0;
}