A 100 watt solar power panel usually costs $146 they are on sale for 0.75 of the regular price what is the sale price

Alidded glass container is filled with a colored gas. after a period of time, it is observed that the gas is uniformly spread throughout the box and that the movement has slowed considerably. next, a warm iron plate is carefully placed under the box. why is there resumed movement of the gas in the container?