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]

}

def average(numbers):

total= sum(numbers)

total=float(total)

return total/len(numbers)

def get_average(students):

homework=average(students["homework"])

quizzes=average(students["quizzes"])

tests=average(students["tests"])

net_average= 0.1*homework+ 0.3*quizzes+ 0.6*tests

return net_average

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"

def get_class_average(y):

results=[]

for x in y:

results=results.append(get_average(x))

return average(results)

it resulted in an error:

Oops, try again. get_class_average([alice]) resulted in an error: 'NoneType' object is not iterable