I was asked a market sizing question to estimate the number of trains required between Dubai and Abu Dhabi (The government was planning to start daily trains between the two cities). My approach was to find out the number of daily travellers to estimate the capacity required. I segmented the travelling population into business and non-business travellers. The frequency of travel would be higher for business travellers compared to non-business travellers. The idea was to identify the proportion of population who would travel for business purposes vs. other purposes. However, I did not have a valid assumption/rationale to find this proportion. I segmented based on age buckets, but after that, I wasn't sure what percentage of the total population would be business/non-business travellers. How would you approach this question?