If a 0.75kg bullet made a 3.0kg block swing to change its height 0.5 meters, how fast was the bullet traveling? (i solved & 15.7 m/s is incorrect for some reason? )

Along wire carrying a 4.2 a current perpendicular to the xy-plane intersects the x-axis at x=−1.7cm. a second, parallel wire carrying a 3.0 a current intersects the x-axis at x=+1.7cm. part a at what point on the x-axis is the magnetic field zero if the two currents are in the same direction? express your answer to two significant figures and include the appropriate units.