My code is generating error prompt . Please , help me look it up.

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 = sum(numbers)
total = float(total)
average = total / len(numbers)
return average
```

""" This function get average for each students and return

the final score for each student"""

def get_average(student):

homework = average(student["homework"])

tests = average(student["tests"])

quizzes = average(student["quizzes"])

`return (0.1*homework + 0.3*quizzes + 0.6*tests)`

""" This function determine the grade for each score passed as an argument"""

def get_letter_grade(score):

```
if score >= 90:
return "A"
elif score >= 80 and score < 90 :
return "D"
elif score >= 70 and score < 80 :
return "C"
elif score >= 60 and score < 70 :
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)

Here is the error message:

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