Antifreeze could also be called “antiboil” because it also raises the boiling point of the water in a car radiator. Hot weather combined with a hot engine can easily raise the temperature of the water in the radiator above 100 °C, which is the boiling point of pure water. If the water boils, it could cause the engine to overheat and become seriously damaged. However, if antifreeze has been added to the water, the boiling point is much higher. For example a 50 percent antifreeze solution has a boiling point of 129 °C. Unless the water gets hotter than this, it won’t boil and ruin the engine.
Alex and Bob both took their cars to a mechanic because they were having engine troubles. The mechanic decided that both need the water in their radiator replaced. The mechanic added a large amount of antifreeze to the water he put into Alex's radiator. Because he wanted to save money, the mechanic only added a small amount of antifreeze to the water he placed into Bob's radiator.

Which person's engine, Alex's or Bob's, is less at risk of becoming damaged if it becomes very hot?