Please answer me 11 numerical

Dear student,​​​​
Given,
power of the lens, P= 5D
The focal length of the lens,$f =1/P=( 1/ 5) m =0.20 m = 20 cm$
 image distance, v = 40 cm
According to lens formula:


So the candle should be placed at a distance of 40 cm from the lens so as to form a sharp image on the wall. 

Regards,