Question 1121515
Model A is C=17,000+(40000/20)*3x+200x or 6200x+17000; 5 years, this is $48,000; 4 years: $41,800
Model B is 25000+(40000/35)3x+400x=3828.57x+25000; 5 years, this is $44,142.85; 4 years: $40,314.28

{{{graph(300,300,-5,8,-2500,60000,6200x+17000,3828.57x+25000)}}}
For any year, put that number into x for each.
They are equal when 6200x+17000=3828.57x+25000
2371.43x=8000
x=3.37 years

Double the cost of gas and A will be 17000+12200x and B will be 25000+6857.14x. It would make the Model B a better overall buy much sooner.
{{{graph(300,300,-5,8,-2500,60000,12200x+17000,6857.14x+25000)}}}