Probability of sitting in the aisle based on the plane ticket's letter

Suppose a plane denotes their seat assignments in the format: row number - seat letter. For example, ticket 12-B would denote seat B in the 12th row of the plane.
Given this information, along with the following details regarding the layout of the plane...

• The first 10 rows are first class seats and contain 2 seats per row
• The next 20 rows are business class and contain 4 seats per row
• The final 80 rows are economy class and contain 8 seats per row

...calculate the estimated probability that a given seat letter (e.g. A, B, C, D, etc) is an aisle seat.

Note that given the above information around the layout of the plane, you'll need to make some logical assumptions around how the seats would be configured, as well as the ordering of the seat letters. There is no 'correct' answer here (it depends on your assumptions), but you should focus on creating a well-reasoned/logical analysis to return the probability of an aisle seat by seat letter based on the assumptions you lay out.