Riding a Ferri wheel physic problem(help)

[SkyRequiem]

Homework Statement

A student of weight 656 N rides a steadily rotating Ferris wheel (the student sits upright). At the highest point, the magnitude of the normal force N on the student from the seat is 581 N. (a) What is the magnitude of N at the lowest point? If the wheel's speed is doubled, what is the magnitude FN at the (b) highest and (c) lowest point?

Homework Equations

F=(mV^2)r a=v^2/r

The Attempt at a Solution

here are my "guesses", becuase i am so confused...
Fn is same as the centripetal acceleration, which is doward to the center of the wheel.
m=66.939 Fg = 656N
-581-656=66.939(-a) what I don't get is that if Fn= a, then this equation is not valid, i mean 581=a? I used this equation becuase it looks like the one in the textbook, but I didnt really get the equation.

 

[SkyRequiem]

this problem is solved, so nvm