Which of the units of the following physical quantities are derived

Which of the following changes to a pipe would increase the conductance by a factor of 12? 1.quadrupling the length and tripling the radius.2.reducing the length by a factor of and doubling the radius.3.tripling the length and reducing the radius by a factor of .4.reducing the length but a factor of and doubling the radius.

8. why do radio telescopes convert radio waves (analog signals) to electrical (digital) signals for analysis? (hint: what did the article say about the advantages of digital signals? )

Stars x and y are both bluish main sequence stars. star x has a higher absolute brightness than star y. how do the two stars compare? explain