Mimi has a pot that contains 7 liters of brine(salt water) at a concentration of 50 grams/liters. She needs to boil some of the water off to increase the concentration of salt.

A. Construct a model that gives the concentration C of the brine after boiling it. (Let x represent the number of liters of water that Sarah boiled off.)

B. How much water must be boiled off to increase the concentration of the brine to 100 grams/liter?