Process Costing BPP Question

Good Afternoon,

I am struggling on one question in the BPP revision kit.

Q) Ellis Co uses process costing to value its output. The following was recorded for the period:

Input materials 2000 units at $4.50 per unit
Conversion costs 13,340
Normal loss 5% of input at $3 per unit
Actual loss 150 units

There were no opening or closing inventories.

What was the valuation of one unit of output to one decimal place?

The calculations from the book says:
Input = 2000 x 4.50 = 9000
Conversion = 13340
Normal loss = 5% x 2000 x 3 = 300
Expected = 2000 – 100 = 1900

Please can you explain where the 100 units came from at the expected section?

Many thanks,