The given table categorises the house types and the number of bedrooms.
Development Houses
2 Br 3 Br 4 Br Total
Single-Family 5 19 34 58
Townhouse 24 42 30 96
Total 29 61 64 154
A daycare centre is planning to distribute pamphlets to the families with children living houses with three or more bedrooms, due to budget. In addition to sending out flyers, it also decides to send out invitations for a free day of daycare, to the family residing in two categories with the most houses. If a house that already received a flyer is chosen at random to receive the second stage of the marketing, then the probability that the house belongs to one of these two groups is pq, where p,q are co-primes. What is the value of q−p?