It has been celebrated recently that hydrogen fuelled buses are being introduced into London. This is because the use of hydrogen as a fuel is better for the environment as there are no emissions of carbon dioxide. The new buses carry the same number of passengers and will be travelling exactly the same routes as the ones that they are replacing. However, commercially sold hydrogen is produced from natural gas. The process to produce one tonne of hydrogen from natural gas puts, on average, eight tonnes of carbon dioxide into the atmosphere, whereas the production of fuel for the existing buses does not emit any carbon dioxide. The further costs of transporting the fuel to the bus depot also need to be considered. We should therefore not welcome the introduction of these buses. Given that the following extra information is available: 1 The distance that each type of bus can travel using one tonne of fuel. 2 The distance that each bus needs to travel every week. 3 The amount of carbon dioxide emitted when the existing buses use one tonne of fuel. 4 For each type of fuel, the amount of carbon dioxide emitted in transporting one tonne of fuel to the bus depot.