Can you recommend a good source that explains this topic in detail?

I need to solve this question too

4. Steelco uses coal, iron and labor to produce 3 types of steel. The inputs for one ton of each type of steel are shown in the following table. Up to 200 tons of coal can be purchased at a price of $10 per ton. Up to 60 tons of iron can be purchased at $8 per ton and up to 100 labor hours can be purchased at $5 per hour. Xi= tons of steel 1 prouuced maxz=(513085)1+(30205)2+(251085)3 st 31+22+x3200 x1+x360 x1+x2+x3100 Answer the below questions according to the gams report given below. a. What would be the profit if only 40 tons of iron could be purchased? b. What would be the profit if 230 tons of coal could be purchased? c. What is the smallest price per ton for steel 3 that would make it desirable to produce it? d. What would be the profit if steel 1 sold for $55 per ton? e. What would be the profit if steel 2 sold for $28 per ton? f. What would be the profit if steel 1 sold for $48 per ton and steel 2 sold for $28 per ton? g. What would be the new optimal solution if 230 tons of coal and 40 tons of iron are available