Final answer:
Elena being 39 years old in April 2006 is correct if she was born in the winter of 1966. The firm's claim to be 39 years old in April 2006 is incorrect; it should be at least 40 years old by that time, so there's a mistake with the firm's age.
Step-by-step explanation:
The question is related to a possible error in reporting the ages of Elena and the firm. If Elena was born in the winter of 1966 and was 39 years old in April 2006, that is indeed correct because from 1966 to 2006 is exactly 40 years, and depending on the exact month of Elena's birth in the winter of 1966, she could have just turned 39 the winter before April 2006.
However, if the firm claims to be 39 years old in April 2006, there must be a mistake in the firm's age. Even if the firm was founded in January 1966, it would be 40 years old by January 2006. Therefore, the firm's age is a mistake.