error: Oops, try again. get_class_average([alice]) returned 83.8666666667 instead of 91.15 as expected

i don't have idea why this code throw this error

```
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]
}
students = [lloyd,alice,tyler]
# 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"])*0.10
quizzes = average(student["quizzes"])*0.30
tests = average(student["tests"])*0.60
total = homework + quizzes + tests
return total
def get_letter_grade(score):
if score >= 90.0:
return "A"
elif score >= 80.0 and score < 90.0:
return "B"
elif score >= 70.0 and score <80:
return "C"
elif score >= 60.0 and score <70:
return "D"
else:
return"F"
get_letter_grade(get_average(lloyd))
def get_class_average(student):
results = []
for item in students:
results.append(get_average(item))
print results
return average(results) .
```