You have a fix amount of frequencies (= n)
For n frequencies without frequency hopping, you are limited to 3 TRX / sector.
For n frequencies WITH frequency hopping, you can expect to reach 4 TRX / sector.
Of course, this is just an example! In your network, the values are not 3 or 4 TRX / sector. It’s certainly other values, that could be assessed by your planning department.