You were expecting to do 441 kts GS, so at 2010 you had 50/60 x 441 = 367.5 nm to go.
You now have to do this in 55 mins, so required GS is 367.5 / (55/60) = 401 kts
GS must reduce by 40 kts. Wind velocity hasn't changed so the reduction in TAS is also 40kts. Answer b.