The boundary of a lamina consists of the semicircles together with the portions of the x-axis that join them. find the center of mass of the lamina if the density at any point is inversely proportional to its distance from the origin. $ y = \sqrt{{\color{red}4}-x^2}, y = \sqrt{{\color{red}16}-x^2}$

The heater element of a 120 v toaster is a 5.4 m length of nichrome wire, whose diameter is 0.48 mm. the resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10-6 ω·m. the toaster is operated at a voltage of 120 v. (a) what is the power drawn by the toaster? (b) if the cost of electricity is 12 ¢ per kilowatt-hour, and it takes 2 minutes to toast bread, how much does it cost for toasted bread? (c) when the heater element is at room temperature, is the resistivity in the nichrome wire greater than, less than, or equal to it’s resistivity when at operating temperature? explain.