When visiting your grandmother, you decide to take a fresh warm bath and wash your hair. However, grandmother lives in Maine, where the tap water is very soft, having a hardness of only 20 mg/L as CaCO3. In order to have an effective shampoo, you want the hardness to be about 80 mg/L as CaCO3. But, you notice that grandma regularly buys bottled mineral water that has the following concentration of major ions, and you have the crazy idea of using the mineral water to adjust the hardness: Ions mmol/L
Ca2+ 5
Mg2+ 0
Na+ 1
Cl- 1
HCO3- 10
SO42- 0

Required:
If the total volume of the bath tub is 1m3, what volumes of tap and bottled water must you mix together to have your ideal shampoo? If bottled water costs $1 per liter, what bill is grandma going to expect for a bath?