It takes same time for A and B to strike the plane.
Speed is measured as the ratio of distance to the time in which the distance was covered. Speed is a scalar quantity as it has only direction and no magnitude.
When a particle is thrown obliquely near the earth’s surface, it moves along a curved path under constant acceleration directed towards the centre of the earth. The path of such a particle is called a projectile, and the motion is called projectile motion.
So both A and B strikes the plane at same time.
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