Both students i.e. Student 1 and Student 2, had an intention of stargazing at night and knew that a…

Both students i.e. Student 1 and Student 2, had an intention of stargazing at night and knew that a telescope would be required for viewing distant stars. Student 1 visited a shop to purchase the necessary equipment for stargazing and purchased two lenses X and Y, the former being thicker and the latter thinner. On the other hand, Student 2 opted for a different approach. He decided to build his telescope by combining a concave mirror of focal length $25\text{ cm}$ and a plane mirror, along with a convex lens of focal length $5\text{ cm}$. Which lens would Student 1 use as an objective, X or Y?