Revenue: Recognition of profit

I am struggling with recognition of profit for performance/obligation recognized overtime:

BPP revision kit 2021:

Bridgenorth Co case:
B. Co has undertaken a $5 million contract to repair tunnel, contract sign on 1 January x8 and expect to take 3 years. contract measured according % of work completed as certified by the surveyor. The customer gains control of the asset as each stage of the tunnel is completed. B CO. has enforceable right to payment for performance complete to date.
Total contract value: 5000
Costs to date: 2300
Estimated cost to completion: 2100
Work invoiced to date: 2000
cash received to date: 1500
% certified complete: 50 %
Question: what profit recognized

Now there is nearly exactly the same quesiton in BPB revision kit 2020 (just change the % certified complete to 40%).

But there were 2 answers:

in BPP 2021: Answer is
revenue = 50% x 5000 = 2,500
Expenses = -2300
Profit = 200,

While answer in BPP 2020 is: (the actual percentage in BPP 2020 is 40%, I took 50% for easy comparison)
revenue= 50%*5000= 2,500
Expenses= 50%* (2300+2100)= 2,200
Profit = 300

Can you help to advise which way is correct?

Thank you very much