My Eigth Grade Math Homework

The heat lost through a windowpane varies jointly as the difference of the inside and outside temperatures and the window area, and inversely as the thickness of the pane. In one hour, 49.5 joules of heat are lost through a pane 40 cm by 28 cm that is 0.8 cm thick, when the temperature difference is 44 degrees celsius. How many joules are lost in one hour through a pane 0.5 cm thick having an area that is 0.25 times the area of the other pane, when the temperature difference is 40 degrees celcius.

Please help.