premise: Elizabeth de Beauchamp Goudge FRSL (24 April 1900 – 1 April 1984) was an English author of novels, short stories and children's books as Elizabeth Goudge. She won the Carnegie Medal for British children's books in 1946 for "The Little White Horse". She was a best-selling author in both the UK and the US from the 1930s through the 1970s.
hypothesis: She was a best-selling author in the UK and US before she was 30.
reason: She was born in 1900 and was a best-selling author in both the UK and the US from the 1930s through the 1970s, so she was at least 30 [in the 1930s]. The model might not know math.