Here, `f_0 = 1.25 cm, f_e = 5 cm`,
`d = 25 cm, L = ?, M = 30`
When final image is formed at the near point of eye, the magnifying power of compound microscope is given by
`M = (L)/(f_0)(1 + (d)/(f_e))`
`30 = (L)/(1.25) (1 + (25)/(5)) = (6 L)/(1.25)`
`L = (30 xx 1.25)/(6) = 6.25 cm`.