Please show clearly, all work (calculation) and every question for better understanding

You've volunteered to make bird houses, at your own expense and on your own time, to be offered for sale at your daughter's high school fair to raise money for new sports equipment. You have three different designs in mind. You estimate the first design will require about $5 in material cost and about two hours of work. The second design is a little more elaborate and will require about $10 in material cost and three hours of work. The last design, more elaborate yet, will require about $15 in material cost and four and a half hours of work.

There are about 5 weeks remaining until the school fair. You figure you can safely work an average of between 35 and 40 hours per week (week day nights and weekends) and you only have $600 available to complete the project. After doing some expected value calculations, you conclude the best product mix is 25 birdhouses using the first design, 20 birdhouses using the second design, and 15 birdhouses using the third design. You develop a construction plan as follows:

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