Buy out 2017 CX5 or lease 2020?

Hey guys, I have a 2017 CX5 Grand Touring that’s at the end of its lease. My buyout is about 18300 plus tax and it has 40k miles but runs like new. The choice I have to make is this... Buy the car (cash-no financing) or lease a 2020 Grand Touring for $393 a month. (15k miles a year). The cash I have is from cashing out my 401k several years ago to pay for kids colleges that ended up not needing to be spent. If I go the lease route, I’ll probably reinvest the money back into some kind of retirement fund.
If I buyout the 2017, I’ll probably sell it in two yrs with approximately 70k miles, for I’m guessing, around $10k, and put that money towards my next car.

The question is, what do you think would be the best move, and why?
Thanks so much!

I would just do the math and see what works best for you.

I would just do the math and see what works best for you.

Thanks. What’s the equation I should use to do the math?