How Much 35% Reduced Iso-Extract is required to bitter this beer?

Kg of Reduced Iso =
(20 Beer BU's/0.7 Tetra Factor) (20,000HL)
/ (.35 RHO CONC.) (0.70 Util.%) (10,000)
= 233 Kg

The RHO is 70% as bitter as Iso alpha Acid, hence the RHO fact of 0.7.

You would order 233 Kg of Hopsteiner 35% Reduced Iso-Extract.

Utilization post fermentation = 0.70 Kettle Utilization = 0.45

For conversion to barrel use: 1 Barrel = 1.17HL