In this task, you're given a statement, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.

Context: In 1200, Freiburg's population numbered approximately 6,000 people. At about that time, under the rule of Bertold V, the last duke of Zahringen, the city began construction of its Freiburg Munster cathedral on the site of an older parish church. Link Information: Berthold V (1160 Question: How old was Bertold V when the construction of Freiburger Munster began?
Answer: 40