The descent started from FL 220 and not FL 200 as mentioned earlier.
Hence the total vertical distance travelled is 18000 feet.
TAS - 197
Wind - 240/30 (Hence headwind = 30 cosine 60 = 15)
Ground Speed = 197 - 15 = 182 kts
39 NMs travelled at a speed of 182 kts will take 12.85 mins
Hence the ROD will be 18000/12.85 = 1400 ft/min
I have no clue why we get a different answer using the CX2 or the ROD formula. But the above is the way I solved it