Need help with a formula with a value that falls in a range of numbers

I am converting an Excel file to Adobe and am working on the formulas based on Overall Score. I have figured out how to write the formula for the 100% and the 0% bonus, but am having issues figuring out how to get the 80% and 60% answers.
For my 100%, here is the formula:
if (Number(this.getField("Overall score").valueAsString)>199) event.value = "100%";
else event.value = "";
This gives me a blank value if the Overall score is less than 200, which is what I want. I need to figure out how to get the 80% value if the overall score is >=180 and <=199, and a blank value if not in that range. I have tried various formulas and either get syntax errors or illegal XML format. Thanks!