The length of the shadow of a vertical tower on level ground increases by 8.4 cm when the altitude of the sun changes from 45° to 30°. What is the height of the tower (in m) ?

$4.2(\sqrt{3}-1)$ $8.4(\sqrt{3}+3)$ $4.2(\sqrt{3}+3)$ $4.2(\sqrt{3}+1)$

$4.2(\sqrt{3}+1)$