Passing XML value in JSON with Variable

I am currently trying to send a request via Postman.

  1. Request content-type has to be application/json

  2. For one of the data objects I would like to pass an XML value. How do i do this in postman request body?

  3. Is it also possible to create a variable for testing purpose where I can pass local XML file reference?

in the Request Pre-request Script

//reset the 'Content-Type header
pm.request.headers.add({key: "Content-Type",value: "application/json"});   

am I understanding your question correctly