Set both capitals, how many months late B arrives, and the profit. The first step does the subtraction on its own line, and the last step prints what the trap reading would have paid B alongside the right answer.
₹21,000 all year, ₹12,000 from month 4
21 : 8 · 10,500 and 4,000
Set the delay to 0 and B is in from day one, so this collapses to Model 1 and the trap comparison disappears. Every other delay reopens it.