Which of the planets is the brightest?

Assuming that the dimmest visible star to the naked eye has a magnitude of about $6$. The brightness of planet Venus (magnitude = $-4$) with respect to this star is ........ times brighter.

The speed of recession of a galaxy is proportional to its distance.

$A$ particular emission line,detected in the light from a galaxy,has a wavelength $\lambda' = 1.1\lambda$,where $\lambda$ is the proper wavelength of the line. The distance of the galaxy from us is:

Hubble's law states that the velocity with which a galaxy is moving away from the Earth is proportional to:

The tail of a comet points