I keep getting this error...

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

I think that everything should print out just like the exercise says it should but it keeps giving me this error. I have tried going back and looking through all of my functions, but they look good and I believe I am passing all of the correct information through each stage as well.

Here is 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]
}
# Add your function below!
def average(numbers):
total = float(sum(numbers))
average = total/len(numbers)
return average
print average
def get_average(student):
homework = average(student["homework"])
quizzes = average(student["quizzes"])
tests = average(student["tests"])
grade = homework*0.1 + quizzes*0.3 + tests*0.6
return grade
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"
elif score < 60:
return "F"
get_letter_grade(get_average(lloyd))
def get_class_average(students):
results = []
for student in students:
results.append(get_average(student))
return average(results)
students = ["lloyd","alice","tyler"]
print get_class_average(students)
print get_letter_grade(get_class_average(students))
```