Context: Sophie is sitting on a roller coaster cart as it reaches the bottom of a big loop. Earth's gravity is pulling down on Sophie with a force of 600N. The seat of the cart is pushing up on Sophie with a force of 1,200N.
Assume all other forces on Sophie are balanced. Which statement describes the forces on Sophie?
A. The forces are balanced, so there is no net force on Sophie.
B. The forces are unbalanced, so there is a net force on Sophie.
Determine the correct option from the provided choices and reply with its corresponding letter.

B