why is my class letter grade A instead of B when the class average is 83.866667?

```
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)
result = total / len (numbers)
return result
def get_average(student):
homework = average (student ["homework"])
quizzes = average (student ["quizzes"])
tests = average (student ["tests"])
sum = .1 * homework + .3 * quizzes + .6 * tests
return sum
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)
students = [lloyd, alice, tyler]
print get_class_average (students)
print get_letter_grade (students)
```