What is the mean of 22, 72, 79, 72, and 70

What happens when a rubber rod is rubbed with a piece of fur?

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?

Which of the following are forms of phase changes a. freezing b. condensation c. heating d. exchanging