why we do not consider the market value of the shares of splinter (fair value)

Plank acquired 60% of the issued equity share capital of Splinter on 1 January 20X2. On that
date, Plank paid $3 cash per share acquired and also issued two shares (nominal value $1 per
share) in exchange for each Splinter share acquired. At the date of acquisition, Splinter had
ten million equity shares of $1 nominal value in issue, plus a share premium account balance
of $10 million and had retained earnings of $50 million. The fair value of the non?controlling
interest in Splinter at the date of acquisition was $14 million. The fair value of an equity share
in Plank and Splinter were $4.50 and $1.50 respectively at 1 January 20X2.
What was goodwill on acquisition of Splinter for inclusion in the consolidated financial
statements of Plank for the year ended 31 December 20X2?

18+54+14=86 – (1×10)-10-50 =16m {but why not (1.5×10) fair value of shares instead of (1×10)}