Under conditions of constant drying rate, a flat sheet measuring 25 cm*25 cm*1 cm and weighing 14 kg was dried initially from one side. When the sheet was reduced to 10 kg in weight, it took 5000 seconds. Using the same materials, a second flat sheet measuring 7 m*7 m*1 cm must only be dried from one side. The amount of time it took for the object's weight to decrease from 1.5 kg to 1.3 kg under the same constant drying conditions (measured in seconds).