That Constant Double to Float newbie thing

Hi, newbie here. I am reading my first C book and I am attempting to compile the code so I can write it as I practice. I googled this error and it told me to put an " f " after %.07 sales tax which gives me a whole new set of errors. If I copied the code straight out of the book why am I having problems? Also I was wondering if the tabbing is correct in this code so I know I am doing it right.

Thanks :)

Code:

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/* Computes net tire sales */
#include <stdio.h>
main()
{
        int numTires;
        float tirePrice, beforeTax, netSale;
        float taxRate = .07; /* Sales Tax */
        /* Ask user for values */
        printf("how many tires bought? ");
        scanf(" %d", &numTires);
        printf("How much is each tire? ");
        scanf(" %f", &tirePrice);
        /* Computer the Sale */
        beforeTax = tirePrice * numTires;
        netSale = beforeTax + (beforeTax * taxRate);
        printf("Your total sale is %.2f\n", netSale);
        return 0;
}

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Code:

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float taxRate = .07f; /* Sales Tax */

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Thanks, for some reason the book doesn't write it like that? Whats the deal! It's Sams!