$6.$ Assume you are observing a variable star that exhibits variations of $60$ s and longer with an amplitude of $0\mathrm{.}02$ magnitudes. At one setting, the readout time of your CCD camera is $17$ s and the read noise is $4$ electrons. At another setting the readout time is $2$ s and the read noise is $6$ electrons. In $10$ s $,$ the star produces $1500$ counts. Assuming the gain is $3$ electrons per count and the sky counts can be neglected, which is the preferred setting?