Actually the first question is not too fair. The service ceiling is set by the manufacturer, and is the max alt to which the a/c is certified to fly at. It will usually be set at a lower altitude that the maximum altitude attainable by the a/c to allow for varying temperatures/density/humidity/etc. Soooo, in theory it shouldn't change.
However, I agree with Gengis in that a drop in temp will allow the a/c to operate at a higher altitude.
Badly worded IMHO.
