$1.$ Convert the following BNF grammar to EBNF:

$1<$ definition $>$ :$=<$ identifier $>=<$ expression $>$

$2<$ expression $>$ :$=<$ term $>+<$ expression $>|<$ term $>-<$ expression $>|<$ term $>$

$3<$ term $>$ :$=<$ factor $>*<$ term $>|<$ factor $>/<$ term $>|<$ factor $>$

$4<$ factor $>$ :$=(<$ expression $>)|<$ number $>|<$ identifier $>$

$5<$ identifier $>$ :$=<$ letter $>|<$ letter $><$ identifier $>$

$6<$ number $>$ :$=0|1|2|...|9$

$7<$ letter $>$ :$=$ a $|$ b $|...|$ z $|$ A $|$ B $|...|$ Z

$2.$ Convert the following EBNF to BNF:

$1<$ list $>$ :$=<$ element $>\{,<$ element $>\}$

$2<$ element $>$ :$=<$ identifier $>|<$ number $>|(<$ list $>)$

$3<$ identifier $>$ :$=<$ letter $>\{<$ letter $>\}$

$4<$ number $>$ :$=0|1|2|...|9$

$5<$ letter $>$ :$=$ a $|$ b $|...|$ z $|$ A $|$ B $|...|$ Z