BONUS: An outdoor recreation company wants to make its own custom-branded trail mix. To be profitable, it needs to make each 1 lb package for at most $6. The trail mix will mostly be a mixture of peanuts and cashews, and they want to have as high a proportion of cashews as possible. Cashews cost $11/lb and peanuts only cost $3/lb. To taste test, the company needs to make a 40 lb. test batch. Let c be the weight of cashews, in pounds, they should use in the mixture to maximize the proportion of cashews while limiting the overall cost.