Main Agreement ki Sabse Badi Baat - Consideration

Aaj mujhe ek achha feeling aaya. Mainne socha, agar main Contract Law me akele khada hoon to main yahi kuch seekhne ke baad aakar padh raha hoon. Lekin aaj maine "Pre-existing Duty Rule" ka concept finally samajh liya. Is rule ke madhyam se, agar ek contract ke madhyam se koi existing duty puri karne ke liye payment kiya jaata hai, toh wah existing duty ka payment contract ke aadhar par nahin ho sakta. Ye rule mujhe sabse jyada complex le raha tha. Lekin ab main samajh gaya hoon ki yeh rule kyon lagbhag sabse mukhya hai.