I was stuck on this one as well, and revisited it today and came up with a working code that addresses what you and I were both thinking, in that there had to be a way to pull the insurance cost from the prior function and use that in the new function.

Below is my work, I hope it helps and am available if you have any questions.

```
def calculate_insurance_cost(age, sex, bmi, num_of_children, smoker, name):
estimated_cost = 250*age - 128*sex + 370*bmi + 425*num_of_children + 24000*smoker - 12500
print("The estimated cost for " + name + " is " + str(estimated_cost) + " dollars.")
print(estimated_cost)
return estimated_cost
maria_insurance_cost = calculate_insurance_cost(28, 0, 26.2, 3, 0, "Maria")
omar_insurance_cost = calculate_insurance_cost(35, 1, 22.2, 0, 1, "Omar")
charles_insurance_cost = calculate_insurance_cost(38, 1, 50, 3, 1, "Charles")
def difference_insurance_cost(x, y):
diff_cost = x - y
print("The difference in insurance cost is " + str(diff_cost) + " dollars.")
return diff_cost
difference_insurance_cost(omar_insurance_cost, maria_insurance_cost)
```