In this task, you're given a context, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both context and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the context or linked information.

Context: Hillingsø was made a sergeant in the Royal Danish Navy in 1955, but changed to serve in the Royal Danish Army Link Information: none Answer: none
In 1955 which had more total service members, the Royal Danish Navy or the Royal Danish Army?

Context: He was the son of Henry Andrade Harben and the grandson of Sir Henry Harben Link Information: Henry Andrade Harben FSA (12 August 1849 - 18 August 1910) Answer: 26
What is the age difference between Harben's father and grandfather?

Context: The Wealden iron industry in the Weald was the site of the first blast furnace in Britain in 1491, and produced much of Britain's cast iron Link Information: n a blast furnace, fuel (coke), ores, and flux (limestone) are continuously supplied through the top of the furnace, while a hot blast of air (sometimes with oxygen enrichment) is blown into the lower section of the furnace Answer: coke

What materials are used as fuel in the type of furnace first used in the Weald to produce cast iron?