You Believe That You Have a Costless Monopoly

You believe that you have a costless monopoly. Given your estimate of the one day demand for mushrooms:
Q_m = 900 - 100P_m
Where Q_m = servings of fried mushroom and gravy.
If another booth opens next to yours also selling fried mushroom and gravy, but demand remains as above assume the product is undifferentiated) , how much revenue will each of you generate under the Cournot assumption?

A) $900
B) $1600
C) $1800
D) $16000
E) $800