Edmunds is showing that the average selling price of a 2016 C300 in CA is ~13% off MSRP. This quote has a selling price of ~11.5% off MSRP. It should be feasible to negotiate another $1,000 off for a selling price of $36,788.
If you qualify for Tier 1 credit, insist on a MF of .00152. Auto-pay lowers the MF to .00142.
With the changes listed above, the lease payment should be $365/mo+tax with ~$1,800 drive-off.
If you place 10 security deposits, then the MF drops to .00072, which results in $320/mo+tax with ~$1,800 drive-off + $4,000 security deposit. Up to you if it’s worth saving $1,620 over the course of the lease by lending Mercedes $4,000.