Desublime MATHS CLASS

Intelligent minds are truly leaving education sector. If we still don't know this as a teacher. Someone sent this

I saw in WASP text book on Roman Numeral.

And this is the question: Write in Roman Numeral

CMDXXIV

The text book expressed it, this way then gave the answer as:
CMDXXIV
CM= 900
D=500
XX=20
IV=4
CM+D+XX+IV= 1420.

My question is it right to say CMDXXIV =1424

I thought 1424 is = MCDXXIV

DIFFERENTIATION 3: FUNCTION OF A FUNCTION (CHAIN RULE)