I am stuck on Exercise 9/10 which can be found HERE

The error it gives is:

Oops, try again. One of the following is missing or broken when we tried to use it: alice, lloyd, tyler, students, get_class_average, get_letter_grade

In the Output Screen, it doesn't give any errors, and does exactly what it is supposed to. But, it won't let me move onto the next exercise.

```
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)
return total/len(numbers)
def get_average(student):
homework = average(student["homework"])
quizzes = average(student["quizzes"])
tests = average(student["tests"])
return homework*.1+quizzes*.3+tests*.6
def get_letter_grade(score):
if score>=90:
return "A"
elif score<90 and score>=80:
return "B"
elif score<80 and score>=70:
return "C"
elif score<70 and score>=60:
return "D"
else:
return "F"
def get_class_average(students):
results = []
for student in students:
results.append(get_average(student))
return average(results)
print get_class_average([lloyd, alice, tyler])
print get_letter_grade(get_class_average([lloyd, alice, tyler]))
```

Please help!!!