There is a group of dogs playing in a pet house. Their average weight is 9.5 kg. If 5 dogs with an average weight of 6.5 kg leave the group by getting exhausted and 4 dogs of average weight 12.5 kg join the group, the average of the group increases by 3 kg. How many dogs were there in the group initially?
1
12
2
17
3
11
4
7
5
10