Commodity prices of NaCl and urea are about $0.033/lb for NaCl (as rock salt) and about $0.10/lb for urea. Calculate the cost of treating 1000 lb of ice on a surface to produce a solution that

melts at -3.9 degrees Celsius with each chemical.
I know you use to delta T= mkfi but after i find m idk what to do next please help