Assignment based on business analysis

It started with my intro, then "Do you know Python?" i said yes, then simply reversed the order of the strings (hello world -> world hello) I did it in 2 ways; the interviewer was happy. Then she gave me a small case study about opening a chat shop (basically a chaat chopati type), so how'd you consider all kinds of business parameters before setting it up? Then she gave me a scenario about the Jar app: like the app suggests, its users invest the recommended amount, but the user invests the way he wants, and again the app suggests the same amount... How'd you deal with it?