HELP!!!!

[mejust20]

I'm on level four and my mission is to Erect two Ballista Towers in the west part of town. Other wise the black hordes will atack.
Well the problem is that I built a college for research so I can have the option research construction Gear Wheels .
The only problem is that I can't reserch on gear wheels because that option isn't avalible a not only I have killed all the bad guys but still I can't pass the level because I don't have the tecnology to build ballista towers.
What must I do to have that tecnology to pass .

[mejust20]

I'm on level four and my mission is to Erect two Ballista Towers in the west part of town. Other wise the black hordes will atack.
Well the problem is that I built a college for research so I can have the option research construction Gear Wheels .
The only problem is that I can't reserch on gear wheels because that option isn't avalible a not only I have killed all the bad guys but still I can't pass the level because I don't have the tecnology to build ballista towers.
What must I do to have that tecnology to pass .

[mejust20]

to have gear wheels tec , it requires construction and stronghold tec. I have construction available but no stronghold. Know what HELP

[mejust20]

Heyyy!!!!! I found the solution by myself
http://forums.ubi.com/images/smilies/35.gif

[BLC_Sky]

It is because of our positive radiation http://forums.ubi.com/images/smilies/35.gif