Profit is Shs. 3000 on a ring and Shs. 1900 on a chain. With $x$ rings and $y$ chains, the objective function to maximise is:

1. The objective function totals the profit earned across both products. 2. Rings contribute $3000$ shillings each, so $3000x$. 3. Chains contribute $1900$ shillings each, so $1900y$. 4. Adding gives $f(x,y)=3000x+1900y$, to be maximised. 5. The version reading $1900x+3000y$ attaches each rate to the wrong product, and $4900(x+y)$ assumes a ring and a chain are always made together. _Source: NECTA ACSEE 2023 Advanced Mathematics 142/1, Question 3: Linear Programming_