The correct option is B 2 and 8
Let the two lenses have focal length f1 and f2 meter
In contact, 1F=1f1+1f2= power =10
or, f1+f2f1f2=10.................... (i)
For a separation of d=0.25 m,
1F′=1f1+1f2−df1f2=6
or, 10−df1f2=6
or, f1f2=116 ........................ (ii)
Using (ii) in (i), we get: f1+f2=10×f1f2=1016=58
or, f2=58−f1 .................... (iii)
Using (iii) in (ii), we get: f1(58−f1)=116
or, f1(10−16f1)=1
or, 16f21−10f1+1=0
or, f1=12 or 18
⇒ f2=18 or 12
So, the power of the lenses are 2 and 8 dioptre.