Question 1196973
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It is the total cost divided by the total mass.


Total cost is  $2*100 + $4.50*150 = 2*100 + 4.50*150 = 875 dollars.


Total mass is 100 oz + 150 oz = 250 oz.


So, your <U>ANSWER</U> is  {{{875/250}}} = {{{25/10}}} = 2.50 dollars per ounce.    
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Solved, with full explanation.