Nested Function in python, when I run it, the result came out is NameError. Can anyone help me?

Question

def area(shape, length):
    def circle(radius):
        return(3.14 * (radius ** 2))
    def square(length):
        return(length ** 2)
    return shape(length)
print(area(circle, 10))
print(area(square, 5))

Answer 1

def area(shape, length):
    def circle(radius):
        return(3.14 * (radius ** 2))
    def square(length):
        return(length ** 2)
    return shape(length)
print(area(circle, 10))
print(area(square, 5))

Answer 2

def area(shape, length):
    def circle(radius):
        return(3.14 * (radius ** 2))
    def square(length):
        return(length ** 2)
    return shape(length)
print(area(circle, 10))
print(area(square, 5))

Answer 3

def area(shape, length):
    def circle(radius):
        return(3.14 * (radius ** 2))
    def square(length):
        return(length ** 2)
    return shape(length)
print(area(circle, 10))
print(area(square, 5))