Price per kilometre (leasing)? Corolla BJ 04, used price ~ 13,000 EUR

Hello together, before I take the long way to my Toyota dealer and possibly unnecessarily annoying, I wanted to contact the community for information. The following facts: I bought a Corolla 1.6 (BJ 04) by leasing about 28 months ago, the car would have cost around 11.500 EUR in cash. 3.500 EUR were down payment, i.e. a leasing amount (I hope to call it so) of 9.500 EUR (incl. interest, processing fee etc.). The contract runs for 4 J. Unfortunately, after about half of the running time, I already see clearly that I will drive far more than these 4*15,000 km for professional reasons, 20,000 per year would have been more realistic. I am now preparing for an additional payment for the multi-kilometres, unfortunately I see in the documents that the car dealership handed me at that time not a word of a price per multi-kilometre, a possible tolerance or sons On the Internet there is only what of 2.500 km which are not taken into account upwards and downwards. Can someone, based on my basic data, tell me how high the price per multikilomter will be? I have already found everything possible on the Internet, from 25 cents per kilometer with a polo up to 8 cents for a VW Phaeton, which can probably not be quite somewhere. Thank you already for your help!