Vector a Has a Magnitude of 3

Multiple Choice

Vector A has a magnitude of 3.0 units and makes an angle of −90.0º with the positive x-axis. Vector B has a magnitude of 4.0 units and makes an angle of −120º with the positive x-axis. What is the magnitude of the vector sum A + B?

A) 1.0 units
B) 6.8 units
C) 7.0 units
D) 5.0 units