A Car Heading North Suddenly Collides at an Intersection with a Truck

Multiple Choice

A car heading north suddenly collides at an intersection with a truck of the same mass heading east. If they lock together and travel at $28 \mathrm {~m} / \mathrm { s }$ at 15° north of east just after the collision, how fast was the car initially traveling?

A) 14 m/s
B) 7 m/s
C) 28 m/s
D) 11 m/s