what will it cost to heat 1.5Mg of water from room temperature to 90degrees celcius using electricity at 60% efficiency?

I am assuming that Mg is Megagrams, not milligrams, and that "room temperature" is 21 C

(1/0.6)*(1.5*10^6 g)*(1.0 cal/gC)*69 C
= 1.73*10^8 cal

There is no reason that heating of water cannot be more efficient than 60%, but that is what I assumed wnen using the 1/0.6 factor