6. Consider the three straight, infinitely long, thin wires. These wires having the same line mass density are equally spaced with a separation D fixed in place and each wire carries a current I out of the page as shown in the figure. < I -D 04 D I xe (a) Along the x-axis, find the location(s) where the magnetic field vanishes. < (b) When the middle wire is rigidly displaced by a small distance y ( < < D) along the positive y- direction while the other two wires are still fixed in place, find the angular frequency w of the simple harmonic motion of the middle wire in terms of , D, and I.