A proton is located at (0,0,-3.5x10⁻⁹). What are the Cartesian coordinates of its position?
a) (0,0,-3.5x10⁻⁹)
b) (0,0,3.5x10⁻⁹)
c) (0,0,0)
d) (0,0,-7x10⁻⁹)