Medical Insurance Project (+= operator)

From steps #4 onward, my insurance_cost is not updated after I use the ± operator.
Any help? I’m using Mac OS.

# create the initial variables below
age = 28
sex = 0
bmi = 26.2
num_of_children = 3
smoker = 0

# Add insurance estimate formula below
insurance_cost = 250 * age - 128 * sex + 370 * bmi + 425 * num_of_children + 24000 * smoker - 12500

print (insurance_cost) >>> output is 7000

# Age Factor
age += 4
print (age) >>> output is 32 (+= operator worked)
print (insurance_cost) >>> output is 7000 (apparently ignores the new age)

https://www.codecademy.com/paths/data-science/tracks/dscp-python-fundamentals/modules/dscp-python-syntax/projects/ds-python-syntax-project

You have to save it (the new variable) as new_insurance_cost = _____whatever the formula is here___
(this is stated in step 5)

You already declared the insurance_cost variable, which will use the previous inputs.