Answer:
42,650 kg of calcium carbonate will be produced everyday.
13,600.5 kg of magnesium hydroxide will be produced everyday.
Explanation:
Concentration of calcium ions = 46.9 mg/L
Concentration of magnesium ions = 14.8 mg/L
Volume of solution treated everyday , V= 80 million gal
= 
1 gallon = 4.546 Liter
Mass of calcium ion in V = 
= 
1 mg = 0.001 g

Moles of calcium ions = 
From 1 mole of calcium ion 1mol of carbonate is formed . then from 426,500 moles of calcium ion will form :
of calcium carbonate
Mass of 426,500 moles of calcium carbonate:
426,500 mol × 100 g/mol = 42,650,000 g = 42,650 kg
Mass of magnesium ion in V = 
= 
= 
Moles of magnesium ions = 
From 1 mole of magnesium ion 1 mol of magnesium hydroxide is formed . then from 224,250 moles of magnesium ion will form :
of magnesium hydroxide
Mass of 224,250 moles of magnesium hydroxide:
224,250 mol × 58 g/mol = 13,006,500 g = 13,006.5 kg
42,650 kg of calcium carbonate will be produced everyday.
13,600.5 kg of magnesium hydroxide will be produced everyday.