Unsure when I enter the following code I get an answer out (which I think is correct) but I also get an error. code is:

```
def average(numbers):
total= sum(numbers)
total=float(total)
total=total/len(numbers)
return total
def get_average(student):
homework=average(student["homework"])
quizzes=average(student["quizzes"])
tests=average(student["tests"])
score=0.1*homework+0.3*quizzes+0.6*tests
return score
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"
print get_letter_grade(get_average(lloyd))
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]))
```

Error 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