NIC, BPP REVISION KIT QUESTION ( please answer )

Sir,
its a question from BPP revision kit and I have a doubt in small part of question
DOUBT-1
(227)ALIMAG LTD
(1) Gamila will withdraw gross directors remuneration of GBP 25,000
(2) Gamila husband magnus will become 25% shareholder in Alimag ltd
(3) Alimag limited will then pay dividend of 75,000 to gamilla and 25,000 to magnus
REQUIRED
calculate income tax and NIC payable by gamila and magnus
NIC PAYABLE (AS GIVEN IN REVISION KIT BPP)
CLASS1 25,000-8424*12%=1,989
CLASS1 25,000-8424*13.8%=2,287
MY DOUBT- Why we dont take dividend income into consideration while calculating nic ?
DOUBT-2
OT CASE -TAY LTD
Recived cash and shares on takeover of grey ltd. Tay ltd had acquired 20,000 shares in grey ltd.The shares had an indexed cost in sept 2018 of 96,000 when grey ltd was taken over by kline plc on take over tay ltd got one GBP 1 ordinary share in kline plc worth GBP 4 per share and GBP 2 in cash for each one share in grey ltd
REQUIREMENT;calculate the chargeable gain
the chargeable gain
(20,000*4)+(20,000*2) = 120,000
COST = (96000)
chargeable gain = 24000
but the answer is 8000 WHY NOT 24,000
(ANSWER GIVEN AS IN BPP)
MARKET VALUE INDEXED COST GAIN
20,000*4= 80,000 64000 16000
20,000*2= 40,000 32000 8000
TOTAL 120,000 96,000
MY DOUBT= WHY ONLY 8,000 CONSIDERED AS GAIN WHY 16000 IS NOT CONSIDERED AS GAIN ?