Claudia Asked: How much Treadmill work would I have to do to lose 5kg in a month?

Okay, so I'm 15 years old, and weigh 54 kilos, and am roughly 154 centimetres tall. My goal/dream weight is around 46-48 kilos, and I'm hoping to lose around 5 kilos in a month. I've been really sick the last year, (super long story) so my fitness has just gone bang and disappeared. I want to start the first month off by just doing some treadmill stuff.
So I guess my question is, how much time would I have to spend on the treadmill daily to reach my goal of a 5 kilo weightloss in a month?
Yes Im aware that my diet must change as well, I'm planning on having a daily calorie consumption of about 1200 calories a day, nothing more, and basically burning all that off and a bit more with the treadmill work, and then working from there.
So like I said earlier, roughly how much treadmill work would I have to do per day to reach my goal?
Any help is much appreciated! (: (: