Answer
It is bowed outward.
Work Step by Step
In this case the bottom is the place which is heated the most. We know that the change in temperature is proportional to change in length or volume. So , a lot of heat and high temperature means that bottom will start to expand more. It will expand more than the rest of region, because there's maximum heat.
This process makes that it is bowed outward, because it will expand more than any other region.
