C43 AMG Deal Check

Hey guys, rookie been reading up past month or so and trying to secure a deal:

2020 C43 AMG Sedan
MSRP: ~$70k
Dealer discount: 15%
Months: 42
Annual Mileage: 10,000
Residual: 57%
MF: 0.00139
MSDs: 10

Monthly coming out to $599 pretax

Link to calculator? What’s the monthly payment? Why not 36 months?

I bought mine in may, Msrp was 64k, got about 10% off, NY taxes and no msds means my payment was 720