Two planes, A and $B,$ are flying at the same altitude. Their velocities are $v_A=500k\frac{m}{h}$ and $v_B=640k\frac{m}{h}$ such that the angle between their straightline courses is $=60.($Figure $1)$

Part A

Determine the magnitude of the velocity of plane $B$ with respect to plane $A.$

Express your answer in kilometers per hour to three significant figures.

Part B

Determine the direction angle of the velocity of plane $B$ with respect to plane $A,$ measured counterclockwise from the positive $x$ axis.