Given the following context free grammar, parse the string $a+a**b$ using the CKY parsing algorithm. Build a CKY parsing table for the string. Determine whether the string is accepted or not. After the parsing of the string, identify$/$list all other substrings that are determined to be valid$/$accepted for the grammar.

CFG:

$SS+S|S-S|S**S|N|$

$Na|b|c$