100 items 100 baskets divisor association analysis problem
a) The items that are frequent are $\{1,2,3,4,5,\dots,20\}$ because these all appear in at least 5 baskets.

b) 

(1) $\{5, 7\} → 2$. Then $Confidence=\frac{1}{2}$

hence 5 and 7 will appear together in basket no. 35 and 70 and 2 will appear along with 7 and 5 in basket no. 70 so:

$$ Confidence = \frac{support(\{5,7\}\cup\{2\})}{support(\{5,7\})}= \frac{1}{2} $$

(2) $\{2, 3, 4\}→ 5$. Then $Confidence=\frac{1}{8} $

$\{2,3,4\}$ appear in baskets having basket number multiple of 12 ($LCM\{2,3,4\}$) i.e in basket no $\{12,24,...,60,.....,96\}$ and $\{2,3,4,5\}$ appear together only in basket no 60.

$→ Confidence=\frac{1}{8}$