You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Estonian_language

Context:
Often 'b' & 'p' are interchangeable, for example 'baggage' becomes 'pagas', 'lob' (to throw) becomes 'loopima'. The initial letter 's' is often dropped, for example 'skool' becomes 'kool', 'stool' becomes 'tool'.

Question:
What two letters can be replaced with each other a lot of the time in Estonian?

'b' & 'p'