Bridgenorth Co in Bpp

Bridgenorth has undertaken a $5million contract to repair a railway tunnel.The contract was signed in 1 April 20X8 and the work is expected to take two years.This is a contract where performance obligations are satisfied over time and progress in satisfying performance obligations is to be measured according to % of work completed as certified by a surveyor. Bridgenorth has an enforceable right to payment for performance completed to date

At 31 December 20×9 the details of the contract were as follows
—————————————————–20X9———20X8
Total contract price—————————5000——–5000
cost to date————————————3600——–2300
estimated cost to completion————–700———2100
work invoiced———————————3000——–2000
cash received——————————–2400——–1500
%certified complete————————–75%——40%

What is the contract asset to be recognised at 31 December 2019 ?

Answer: Cost to date: 3600
Profit to date: 525 (5000-400)*0.75
Amounts invoiced: (3000)

Asset = 1125

But in similar situations almost all solutions were: Revenue to date: 5000*0.75 = 3750
Amounts invoiced: (3000)

So what is the calculations based on ? I though it was recognition basis (Output vs Input method), but apparently not.