Stellar Density

5. What should be the faint r band limit for a survey to be able to map the ln ? vs. Z profile out to 100 kpc using main-sequence stars? Assume the same color distribution as for the SDSS sample. For a solid angle of 1 deg2 , how many stars with 0.2 < g - r < 0.4 would you expect with distances between 90 kpc and 100 kpc? Assume whatever additional information you need to solve this problem (not all required information is provided here).