Electric charge is distributed over the disk x^{2}+y^{2}≤1 so that the charge density at (x, y) is σ(x,y)=√x^{2}+y^{2} (measured in coulombs per square meter). Find the total charge on the disk.

^{2}+y^{2}≤1 so that the charge density at (x, y) is σ(x,y)=√x^{2}+y^{2} (measured in coulombs per square meter). Find the total charge on the disk.