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

A