Compute the accurate solution of the given question
Question- Consider a planetary nebula at a distance d. We measure with the Doppler Effect that the shell is expanding at a speed of 25 km/s and find from decade-long observation that the diameter of the nebula increases by 0.75 arcsec per century.
Part 1- Calculate the distance to the nebula in light-years.
I want experts help to calculate the distance to the nebula in lightyears.