#### Answer

$a).$ (1) less than 95%,
$b).$ Height = 3.6m.

#### Work Step by Step

S=4.0m
$v^{2}=u^{2}+2aS=0+(2\times 9.8\times 4)=78.4$
$v=8.85m/s$
95% of impact velocity = ($0.95\times 8.85) =8.4m/s$
Using the same equation of motion,
$0=8.4^{2}-2\times 9.8\times S$
or,
$S=3.6m$
This as a percentage of original height $=\frac{3.6}{4}\times 100=90%$ which is less than 95%.
a). (1) less than 95%,
b). Height = 3.6m.