Getting this error: get_letter_grade(89) returned 'F' instead of 'B' as expected

I'd like to set the parameters to be within the range of 70-79, 80-89, etc. I think that's what's making my code error out. Why do I not need to set exact parameters for that?

```
Replace this line with your code.
lloyd = {
"name": "Lloyd",
"homework": [90.0, 97.0, 75.0, 92.0],
"quizzes": [88.0, 40.0, 94.0],
"tests": [75.0, 90.0]
}
alice = {
"name": "Alice",
"homework": [100.0, 92.0, 98.0, 100.0],
"quizzes": [82.0, 83.0, 91.0],
"tests": [89.0, 97.0]
}
tyler = {
"name": "Tyler",
"homework": [0.0, 87.0, 75.0, 22.0],
"quizzes": [0.0, 75.0, 78.0],
"tests": [100.0, 100.0]
}
# Add your function below!
def average(numbers):
total = sum(numbers)
total = float(total)
total = total / len(numbers)
return total
def get_average(student):
homework = average(student["homework"]) * .1
quizzes = average(student["quizzes"]) *.3
tests = average(student["tests"]) *.6
weighted = homework + quizzes + tests
return weighted
print weighted
def get_letter_grade(score):
if score >= 90:
return "A"
if score >= 80 >= 89:
return "B"
if score >= 70 >= 79:
return "C"
if score >= 60 >=69:
return "D"
else:
return "F"
print get_letter_grade(get_average(lloyd))
```