[tex]4*10 ^{0} =4[/tex] bytes per pixel
[tex]2.5* 10^{6} =2,500,000[/tex] pixels per picture or [tex]1* 10^{7} [/tex] bytes per picture
[tex]1* 10^{9} =1,000,000,000[/tex] so a 200 GB drive is 200,000,000,000
[tex] \frac{200,000,000,000}{10,000,000} = 20,000=2* 10^{4} [/tex]
Hope that helps.
