Kickdrum interview questions

The first question he gave to me, design a cab booking system (he just want a brief about how I'm going to define my entities) Use cases: 1. user can book a ride. 2. user can store favorite locations 3. user can view past bookings 4. new drivers can sign up 5. driver can view past bookings The next question was given an integer N and D I had to add the smallest possible number in N so that N doesn't contain the digit D. Test case1 : N = 100 , D=0, output = 11 Test case2 : N = 5925, D=9, output = 75