monthly service charge is flat. you have to pay it no matter how many therms you use.
since you've used only 25 therms, they'll charge you $0.6686/therm
so, total charge for using 25 therms in one month
= 8.8 + 25*0.6686=16.715+8.8 = 25.52
What is the charge for using 45 therms in one month?
45 = 25 + 20
so for first 25 therms they'll charge u .6686/therm, and rest of the 20 they'll charge u 0.85870/therm
8.8 + 25*.6686 + 20*.85870
25.52+17.174 = 42.694
D is the correct answer is sure
One mole of Na2SO4 is 6.022 * 10^(23) molecules. We can divide this into the quantity in the question to find a value of 1.5/6.022 = 0.2491 moles. Rounded to two significant figures and put in scientific notation, we can rewrite this quantity as 2.5 * 10^(-1) moles
