b
(b) Here, $S = (13.8 \pm 0.2)\,m$ and $t = (4.0 \pm 0.3)\,sec$
Expressing it in percentage error, we have,
$S = 13.8 \pm \frac{{0.2}}{{13.8}} \times 100\% = 13.8 \pm 1.4\% $
and $t = 4.0 \pm \frac{{0.3}}{4} \times 100\% = 4 \pm 7.5\% $
$ = \frac{{13.8 \pm 1.4}}{{4 \pm 7.5}} = (3.45 \pm 0.3)\;m/s.$