Mixed exercise: combining 4 solns of expensive chemical

[den99]

Anybody can help me with this ?

A chemist has four solutions of a very rare and expensive chemical that are 15% acid (cost $120 per ounce), 20% acid (cost $180 per ounce), 35% acid (cost $280 per ounce) and 45% acid (cost $359 per ounce). She requires 200 oz of a 29% acid solution. Find the combination of any two of these concentrations that will minimize the total cost of the mix.

[little_dragon]

Anybody can help me with this ?

A chemist has four solutions of a very rare and expensive chemical that are 15% acid (cost $120 per ounce), 20% acid (cost $180 per ounce), 35% acid (cost $280 per ounce) and 45% acid (cost $359 per ounce). She requires 200 oz of a 29% acid solution. Find the combination of any two of these concentrations that will minimize the total cost of the mix.

U can see how 2 to this here: http://www.purplemath.com/modules/mixture.htm
do how they show
use pairs that make sense (45% & 35% wont mix to 29%, but 20% & 35% can)
find $$ for pairs
pick pair that costs less