Treat this like a Speed sum.

Tom reads at an average rate of 30pph (Tom's speed)
Jan reads at an average rate of 40pph (Jan's speed).

Tom starts at 4:30
Jan starts at 5:20

Tom's time = x
Jan's time = y

x = y + 50 mins

We need to find at what time will they be on the same page (ie at what time would have Tom and Jan covered the same distance).

Distance = speed*time
We have to equate the distances.

x*30 = y*40
30(y+50) = 40y
y = 150 mins or 2hours 20 mins

After 5/2 hours will both Tom and Jan be at the same page.

Jan's time - 5:20 + 2.30 = 7:50

Answer should be D.