If the energy usage of all transportation is 7.10 × 10¹⁴ BTU per year, if their efficiency is to increase by 20%, The new energy usage will be (1 + 20/100)7.10 × 10¹⁴ BTU per year = (1.02)7.10 × 10¹⁴ BTU per year = 7.242 × 10¹⁴ BTU per year.
The energy saved is thus the difference 7.242 × 10¹⁴ BTU per year - 7.10 × 10¹⁴ BTU per year = 0.142 × 10¹⁴ BTU per year.
Since 10⁶ BTU costs $ 20.00, then,
0.142 × 10¹⁴ BTU costs 0.142 × 10¹⁴ BTU × $ 20.00/10⁶ BTU = $ 2.84 × 10⁸ per year = $ 284 million dollars
So the state saves $ 284 million dollars in one year
