The diagram shows quadrilateral ABCD and the bisectors of the angles at A, B, C and D - HSC - SSCE Mathematics Extension 1 - Question 14 - 2018 - Paper 1

First, consider the total combinations for Selector A choosing at least 4 people from 23.

1. The total ways for Selector A can be calculated using the binomial coefficient: $\sum_{k=4}^{23} \binom{23}{k}$

2. Selector B then chooses 4 people from the selected group by Selector A. The number of ways for this is given as: $\binom{k}{4}$ where k is the number of people chosen by Selector A.

3. Therefore, we need to multiply the number of ways Selector A can choose with that of Selector B, leading to a complex form: $\sum_{k=4}^{23} \binom{23}{k} \binom{k}{4}$

4. The overall selection process can be summed across all selections to yield the final count.