What was the main advantage of a dial phone over an operator-controlled switchboard

Apossible explanation for a set of facts that can be tested by further investigation is called

Awave has a wavelength of 7 mm and a frequency of 19 hertz. what is its speed?

On a mild saturday morning while people are working inside, the furnace keeps the temperature inside the building at 23degreesc. at noon the furnace is turned off, and the people go home. the temperature outside is a constant 16degreesc for the rest of the afternoon. if the time constant for the building is 3 hr, when will the temperature inside the building reach 18degreesc? if some windows are left open and the time constant drops to 2 hr, when will the temperature inside reach 18degreesc?