What's the best way to reduce the weight of a car?

We need to reduce the weight of the car we're designing.

So what we'll do is shave 10% off every component.  10% off the wheels, 10% off the engine, 10% off the frame...

OR maybe we'll remove all the passenger seats, the air conditioning unit, the entertainment system, investigate a ceramic engine, carbon fibre frame...

We need to reduce the operating cost of our department.

So what we'll do is ask every team to reduce their budget by 10%.

OR...