20 mil IGB = 100 TBT
10 mil IGB = 50 TBT
5 mil IGB = 25 TBT
1 mil IGB = 5 TBT
200k IGB = 1 TBT
Multiply that buy 39 TBT, and you get 7.8 mil IGB
So for 39 TBT, applying the normal rate, you'd be able to get 7.8 mil. Although if you just offer the TBT for the highest IGB offer, you might be able to get less/more.