A gardener needs at least 10, 12 and 12 units of chemicals A, B and C. Jars cost 3,000 and cartons 2,000. The objective function is:

1. The gardener wants the chemicals at the lowest cost, so the objective is minimisation, not maximisation. 2. Each jar of liquid product costs 3,000, and $x$ is the number of jars, giving $3000x$. 3. Each carton of dry product costs 2,000, and $y$ is the number of cartons, giving $2000y$. 4. The objective function is therefore Minimise $f(x,y)=3000x+2000y$. 5. Attaching each price to the wrong variable, or summing all the given data into $8x+7y+5000$, were both recorded errors. _Source: NECTA ACSEE 2022 Advanced Mathematics 142/1, Question 3: Linear Programming_