$($a$)($i$)$ Differentiate between a half and full adder

$($ii$)$ it is required to add the numbers $6$ and $9$ using a digital computer. Draw a well

labelled diagram of storage registers in block form and adders to accomplish

this task. Hence check that the resulting sum is the number $15$

$($b$)$ Explain with well labelled diagrams what is meant by the following:

Positive $-$ edge triggering

Trailing $-$ edge triggering

Level triggering