Search - Verify and Replace

Hello All,

I am fairly new to Unix and looking for a solution for a below prob
Content of a file x

223001ABCD
2210015ABCD
221007ABCD
2230015ABCD
223004ABCD

I am looking for a way where I need to search in the file
1. First for Unit Code - '223' ( Position 1 to 3)
2. If Position 6 is '1' & Position 7 between '0' & '5'
do nothing
else
Add space on position 6

The Modified output inside file x
22300 1ABCD
2210015ABCD
221007ABCD
2230015ABCD
22300 4ABCD

Good homework assignment!
Easy to solve if your teacher allows you to use 'awk'.

Good luck!