A particle A is projected from the ground with an initial velocity of 10 m/s at an angle $60 ^{\circ}$ with horizontal. From what height h should another particle B be projected horizontally with velocity 5 m/s. so both the particle collide in the ground at point C if both are projected simultaneously $(g=10 m/s^2)$

Question

$ a)\;10 m \\b)\;30 m \\c)\;25 m \\ d)\;15 m $