Magnetic Force between Two Parallel Currents

Two long, straight wires are parallel and $10$ cm apart. One carries a current of $2\mathrm{.}0$ A$,$ the other a current of $5\mathrm{.}0$ A$.($a$)$ If the two currents flow in opposite directions, what is the magnitude and direction of the force per unit length of one wire on the other? $($b$)$ What is the magnitude and direction of the force per unit length if the currents flow in the same direction