The laws of thermal radiation tell us that a star emits light with a total power per unit area that depends only on the star's surface temperature. the formula is power per unit area=σt4 where σ is a constant with a measured value of σ=5.7×10−8wm2×k4 (as usual, m stands for meters and k stands for kelvins.) you can then find the total power (or luminosity) emitted by the star by multiplying its total surface area by the power per unit area. use these facts to calculate the total power emitted into space by a star with a radius of 8.0×108m and a surface temperature of 6500 k. you will need the formula for the surface area of a sphere, which is surface area (sphere)=4πr2

The chart shows the costs and shipping times for materials that a company needs to build a new product. which describes the best trade-off if the company needs to start building their product within the next two years? they should order the domestic materials because it is always best to choose the fastest shipping time. they should order the imported materials because it is always best to choose the lowest cost for materials. since the shipping time is longer, they should order the domestic materials because the additional cost is worth it to get the materials in time. even though the shipping time is longer, they should order the imported materials because they are less expensive and should arrive in plenty of time to build the product.