Revenue from contracts with customers

Hello,

I am struggling with question 4 from OT ACCA F7 Practice Questions related to revenue from customers.

Direct link: https://opentuition.com/acca/f7/f7-chapter-24-questions/

My calculations are:
(1600+2000)x40%=1440
(3700+760)x75%=3345
3345-1440=1905

I don’t understand why there is a loss of (260,000). How do we get this number?
I also do not undersand the cost balancing figure of 3,410,000. Why it isn’t 3,345,000?

Would appreciate any help with this.