I omitted an article and changed the meaning. What's wrong here?
Imagine that we are driving and I have a set of keys in the car's ignition. If I say (1) ''Those are keys which I have'' and then say (2) ''Those are the keys which I use to start my car'' do I use the articles correctly?
1) You know among all the keys which I have those are just one set
2) You know that those keys are the only ones which I use for this particular purpose (to start my car)
And then we got to a cafe and I pull out 20 bucks and say (3) ''that is the money that I have to buy us some coffee'' then you immediately now that the amount of money I'm ready to spend to buy coffee if LIMITED to just 20 bucks and if I say (4) ''that is money that I have to buy us some coffee'' It means that I might have more money to buy us coffee in my car or some other place and we are not restricted by those 20 bucks I just showed you.
Likewise, I might say ''That's money I got after selling my car'' meaning that it's not the whole sum and there are more and taking THE would mean that it's all I got after the deal.