電費計算香港家庭,

the powe of the air conditioner is 2500W and there are 3 air-con.
calculate the total cost of running all the air-conditioners for 100 hours.
the unit cost of electricity is $0.86 for first 400 units, $0.90 for the next 600 units and $1.00 for the next 800 units. (show the calculations.)

thx:)!