Q: Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.
Problem: a shopkeeper sold an article at $ 1800 with 20 % profit. then find its cost price ?
Options: a. $ 1000, b. $ 1500, c. $ 1850, d. $ 1600, e. $ 2000
A:
b