Beginning C guy.... need help on first FUNCTION assignment

This is suppose to calculate the BMI of someone. I have Hints but I still don't really know where to start... Can anyone give me some suggestions?

Code:

// hint: you're going to need to include another library to make the file functions below work right.

/*
 * Task: create a program that reads a bmi file and outputs bmi to stdout
 *
 * The BMI file is formatted like this:
 * 105, 66
 * 104.8, 58.2
 *
 * Where the first column is the weight in pounds and the second column is the height in inches
 *
 *
 * The output should look like this:
 * Height: 66 inches; Weight: 105 lbs; BMI: bla
 *
 */

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("Missing filename. Usage: %s <filename>\n", argv[0]);
    }

    char line[20]; // variable to store one line at a time from the file
    FILE * infile_fp; // variable to store the file pointer
    infile_fp = fopen(argv[1], "r"); // open the file passed on the command line

    // read the file one line at a time
    while (fgets(line, 20, infile_fp)) {
        float weight, height;
        // write a line here that breaks the weight and height out of the string
        // hint, try sscanf()

        printf("Height: %4.2f inches; Weight: %4.2f lbs; BMI: %4.2f\n", height, weight, bmi(weight, height));

 

Function counting BMI

Code:

float bmi(float weight, float height) {
    return (weight * 703) / (height * height);
}

You should end program in case of error

Code:

if (argc < 2) {
    ...
    return -1;
}
...
if (!infile_fp) {
    printf("Error opening file %s\n", argv[0]);
    return -2;
}

sscanf() format in this case

Code:

sscanf(line, "%f, %f", &weight, &height);

 

Correction

Code:

printf("Error opening file %s\n", argv[1]);