How can I figure out fat content in quark cheese? The store next to my house offers a brand of solid quark.

It's really good and tasty, and it says on their website that it's made of whole milk and it's not being stirred during production, so that it remains solid and keeps layered texture.

However its fat content is listed as 4% to 20% on the label. Apparently they don't want to bother with measuring the exact fat content and labeling each batch separately.

My question is: is there an easy way to measure fat content in quark?

By "easy" I mean something I could do at home using readily available equipment and/or chemicals, within like 5 or 10 minutes, and not ruin the whole package of quark in the process.
Do you have access to similar but more precisely labelled brands? I'm thinking you could use them to calibrate a measurement based on density - weigh a precisely measured volume of a couple of brands with a known fat content and interpolate.

It won't be perfect because the composition of the remaining water/protein mix won't be perfectly consistent.