Free cash flow

Hie, MY question is how did they calculate production costs. Where did they get the 2.5

Part of the notes to the question reads…

It is expected that the factory
will be able to produce and sell 80,000 window units per year although, in
the first year, because of the need to ‘run in’ the machinery and its new
workforce, output is only expected to be 50,000 window units. Each
window is likely to be sold for €750, a price that represents a 150% markup
on cash production costs.
The French factory would be set up as a wholly-owned subsidiary

Answer
Workings
(W1) €m Sales revenues
50,000 × 750 (1.06) = 39.75 Year 1
80,000 × 750 (1.06)2 = 67.42 Year 2
80,000 × 750 (1.06)3 = 71.46 Year 3
80,000 × 750 (1.06)4 = 75.75 Year 4
80,000 × 750 (1.06)5 = 80.29 Year 5

(W2) €m Production costs
39.75 ÷ 2.5 = 15.9 Year 1
67.42 ÷ 2.5 = 26.97 Year 2
71.46 ÷ 2.5 = 28.58 Year 3
75.75 ÷ 2.5 = 30.30 Year 4
80.29 ÷ 2.5 = 32.12 Year 5