All solutions here are SUGGESTED. Mr. Teng will hold no liability for any errors. Comments are entirely personal opinions.

(i)
Let X denote the number of batteries with lifetime of at least 100 hours, out of 10.

$X ~\sim~ \mathrm{B}(10, 0.8)$
$\mathrm{P} (X=10) = 0.107$

(ii)
$\mathrm{P} (X \ge 10) = 0.678$

(iii)
Let Y denote number of packs that satisfy the customer, out of 80.

$Y ~\sim~ \mathrm{B}(80, 0.6777995)$

Since $n = 80$ is large, $np = 54.224 > 5, nq = 25.776 >5$
$\Rightarrow Y ~\sim~ \mathrm{N}(54.224, 17.471)$ approximately

$\mathrm{P} (Y \ge 60)$
$= \mathrm{P} (Y \ge 59.5)$ by continuity correction

$\approx 0.103$