I get an error mesage that says "unsupported operand type(s) for *:'noneType' and 'float'

```
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)/len(numbers)
def get_average(student):
homework = average(student["homework"]) * .1
quizzes = average(student["quizzes"]) * .3
tests = average(student["tests"]) * .6
return homework + quizzes + tests
```

please reply and tell me what I'm doing wrong.