[C++]What Am I Doing Wrong?

[wildgoosespeeder]

For a class, I am supposed to compute federal tax based on this information:

If gross pay is:	Federal tax is:
Less than $100	$0.00
$100 or more but less than $500	15% of the gross over $100.
$500 or more but less than $1,000	$60 + 28% of the gross over $500.
$1,000 or more	$200 + 31% of the gross over $1,000.

The code I came up with:
void Employee::ComputeFederalTax()
{
float multiplier = .0f;
FederalTax = .0f;
if(100.0f <= GrossPay && GrossPay < 500.0f)
{
multiplier = .15f;
}
else if(500.0f <= GrossPay && GrossPay < 1000.0f)
{
multiplier = .28f;
FederalTax = 60.0f;
}
else if(1000.0f <= GrossPay)
{
multiplier = .31f;
FederalTax = 200.0f;
}
FederalTax += (multiplier * GrossPay);
}Assume everything is declared and initialized properly.

Output (click to enlarge):

Instructor:	Mine:

For John Morgan, the computed Gross Pay is $2,000.

The instructor output is different than my output. What am I doing wrong?

If I don't get this fixed within this discussion before November 15 at 1:00AM CST, I'll turn in whatever I got because I got less than 12 hours, starting now, to figure this out.

[wildgoosespeeder]

OK, figured it out. I needed an offset of some kind. Declared one to be 0 and then updated the value within each "if" statement to be 100, 500, or 1000 if one of the "if" statements are tripped. Then updated the last computation. Updated:

void Employee::ComputeFederalTax()
{
float multiplier = .0f;
float offset = .0f;
FederalTax = .0f;
if(100.0f <= GrossPay && GrossPay < 500.0f)
{
multiplier = .15f;
offset = 100.0f;
}
else if(500.0f <= GrossPay && GrossPay < 1000.0f)
{
multiplier = .28f;
offset = 500.0f;
FederalTax = 60.0f;
}
else if(1000.0f <= GrossPay)
{
multiplier = .31f;
offset = 1000.0f;
FederalTax = 200.0f;
}
FederalTax += (multiplier * (GrossPay - offset));
}

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Lock it please!