Sorry, but I am not going to record a video just for you 🙂
They have to produce 5,000 shakes (because of the contract) and that used 5,000 grams. They then produce 9,800 cookies (because they give the best contribution per unit) and that uses another 1,960 grams. So in total they are now using 5,000 + 1,960 = 6,960 grams.
There are only 12,000 grams available in total, and so they now have 12,000 – 6,960 = 5,040 grams left,
Each cake needs 0.5 grams, so with 5,040 grams available they can make 5,040/0.5 = 10,080 cakes.
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