I don't really understand that in the last three lines what is wrong!! and this is the error I get:

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

Could anyone help me? Here's my 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]
}
students = [lloyd, alice, tyler]
# Add your function below!
def average(numbers):
total = sum(numbers)
total = float(total)
avr = total/len(numbers)
return avr
def get_average(student):
homework = average(student['homework'])
quizzes = average(student['quizzes'])
tests = average(student['tests'])
return 0.1 * homework + 0.3 * quizzes + 0.6 * tests
def get_letter_grade(score):
if score >= 90:
return "A"
elif score >= 80:
return "B"
elif score >= 70:
return "C"
elif score >= 60:
return "D"
else:
return "F"
std1 = get_letter_grade(get_average(lloyd))
print std1
def get_class_average(student):
results=[]
for item in students:
results.append(get_average(item))
return average(results)
```