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For such questions, always locate accurately the position of the image of the O. Then draw the ray from the image to the observer. To determine the maximum scope of view using the mirror, always use the two extreme edges of the mirror as point of incidences.
The most common mistake is to equate total energy at X equals to total energy at Y. At Y, there is no way to know the speed as the speed varies which depends on the speed at X.
Since the question wants to find the minimum speed at X to reach Y, you should focus on the highest point of the hill. If you can just clear the hill, you will sure reach Y. So you should consider the total energy at the highest point of the hill and assume the ball just barely reaches the top and stops there. Hence at the highest point, the energy of the ball is just GPE and you can find the minimum speed at point X. Any speed higher, you can clear the hill and reach Y.
To solve this question, you need to apply your FLHR. From the image, you will be able to know the orientation of the force F (thumb) and the magnetic field M (first finger).
For the radiation path that goes straight, it indicates that it is not affected by the magnetic field. That means the radiation has no charge, hence it is gamma rays (a type of electromagnetic wave)
For the radiation path that curves upwards, that means there is a force acting to the top of the image. So orientate the FLHR according and the 2nd finger (convention current) points to the right.
Note the the direction of the convention current is the path in which a positive charge will take, so the radiation must be positive charge, i.e helium nucleus (alpha particles).