I have no idea what i did wrong, and why it does not work as it shoud.

Please help me and point my mistake.

error message : Oops, try again. grades_variance([4, 0, 2, 3, 3, 0, 3]) returned 6129.9152578191 instead of the expected: 2.1224489796

and i get output of this code: 334.071005917

None

```
grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5]
def print_grades(grades):
for grade in grades:
print grade
def grades_sum(grades):
total = 0
for grade in grades:
total += grade
return total
def grades_average(scores):
sum_of_grades = grades_sum(grades)
average = sum_of_grades / float(len(grades))
return average
def grades_variance(scores):
average = grades_average(grades)
variance = 0
for score in scores:
variance += (average - score)**2
variance = variance / len(scores)
return variance
print(grades_variance(grades))
```