Cant mark tasks as complete on Python Syntax: Medical Insurance Project

Although I think my code is propery written with the correct sintax (it´s giving me coherent results) I cant mark tasks as complete

I´m completely lost, I havent even written the variables propery?

Only task 3 is market as complete

# 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("This person's insurance cost is " + str(insurance_cost) + " dollars.") # Age Factor age += 4 new_insurance_cost = 250 * age - 128 * sex + 370 * bmi + 425 * num_of_children + 24000 * smoker - 12500 change_in_insurance_cost = new_insurance_cost - insurance_cost print("The Change in cost of insurance after increasing the age by 4 years is " + str(change_in_insurance_cost) + " dollars.") # BMI Factor age = 28 bmi += 3.1 new_cost_bmi = 250 * age - 128 * sex + 370 * bmi + 425 * num_of_children + 24000 * smoker - 1250 change_cost_bmi = new_cost_bmi - insurance_cost print("The change in estimated isnurance cost after increasing BMI by 3.1 is " + str(change_cost_bmi) + " dollars.") # Male vs. Female Factor bmi = 26.2 sex = 1 new_cost_sex = 250 * age - 128 * sex + 370 * bmi + 425 * num_of_children + 24000 * smoker - 1250 change_cost_sex = new_cost_sex - insurance_cost print("The change in estimated cost for being male instead of female is " + str(change_cost_sex) + " dollars") # Extra Practice num_of_children = 0 new_cost_0_kids = 250 * age - 128 * sex + 370 * bmi + 425 * num_of_children + 24000 * smoker - 1250 change_cost_0_kids = new_cost_sex - new_cost_0_kids print("The change in estimated cost being a male with 3 kids compared to 0 kids is " + str(change_cost_0_kids) + "dollars")