You will be given a definition of a task first, then some input of the task.
Use a disfluent question or a proper question and find the answer to the question based on the given context or return None if an answer can't be found. A disfluent question is a question that has some interruptions in it while framing. A proper question is the correct form of the question without any disfluency.

proper question: How are the forces derived from fields treated similarly to? 
 disfluent question: What type er how are the forces derived from fields treated similarly to? 
 context: The notion force keeps its meaning in quantum mechanics, though one is now dealing with operators instead of classical variables and though the physics is now described by the Schrödinger equation instead of Newtonian equations. This has the consequence that the results of a measurement are now sometimes quantized, i.e. they appear in discrete portions. This is, of course, difficult to imagine in the context of forces. However, the potentials V(x,y,z) or fields, from which the forces generally can be derived, are treated similar to classical position variables, i.e., .
Output:
classical position variables