What’s the answer? Because I can’t find it out myself

Identify a1 and r for the geometric sequence an= -256(-1/4) n-1

This is a map of the mars exploration rover opportunity predicted landing site on mars. the scale is 1cm : 9.4km. what are the approximate measures of the actual length and width of the ellipse? i mostly need to know how to set it up : )

I’m still confused on how to work the percentages