Can someone please check my work for me? (Physics)?

I am giving a speech on E=mc2 and I need to make sure the calculations I did are correct. Basically, I wanted to put it in perspective on how much energy 8oz of water (approximately 0.236kg) contains if converted into pure energy using E=mc2.

I used some online converters for units and I did a bit of rounding for simplicity:

● Energy in 8 ounces of water:

8 ounces = approximately 0.236 kilograms

C (speed of light) = 300,000,000 meters per second

E = mc2 Energy = mass (in kilograms) x (speed of light squared)

E = (0.236 kg)(300,000,000 m/s)2 = 21,240,000,000,000,000 Joules

●Number of cars the above energy can lift to 1 mile (1609.344 meters)

1 average car = 2 tons (4000 pounds) or 1814.369 kilograms

Work (in Joules) = Force x Distance Distance = 1609.344 meters

Force = mass x acceleration (in this case, acceleration of gravity, or 9.8 m/s2)

Work = mass x acceleration of gravity x Distance x number of cars

Number of cars = [Work (Energy from previous problem)] / [(1814.369kg)(9.8m/s2)(1609.344m)] = 742,256,372 cars

So basically, 8 ounces of water, if converted into pure energy, can lift 742 billion cars 1 mile off the ground? This didn't seem right, so I thought I'd ask.

Thanks!