The ocean current the question talks about is the following:
"The Gulf Stream moves northward off the east coast of the United States at a speed of up to 3.5 m/s. Assume that the current flows at this maximum speed and that the earth's field is 50 μT tipped 60° below horizontal. "
The situation is represented in the picture attached.
In order to find the direction of the magnetic force (Lorentz's force) you need to use the rule of the right hand: since the charge moving is negative, you need to place your thumb in the opposite direction of the velocity, while you need to place the other fingers in the same direction of the magnetic field. The magnetic force's direction will be perpendicular to your hand and the sense will be exiting the palm of your hand (and the sheet).
