Final answer:
The infinitive stem of "caber" for the future and conditional tenses is "cabr-", which is used with the appropriate endings for these tenses.
Step-by-step explanation:
The infinitive stem of the verb caber in the future and conditional tenses in Spanish is cabr-. When conjugating caber in these tenses, you would use this stem followed by the appropriate endings. The infinitive stem of "caber" for the future and conditional tenses is "cabr-", which is used with the appropriate endings for these tenses.
For example, in the future tense, the forms would include cabré (I will fit), cabrás (you will fit), cabrá (he/she/it will fit), etc., and in the conditional tense, you would have cabría (I would fit), cabrías (you would fit), cabría (he/she/it would fit), and so on. The infinitive stem of "caber" for the future and conditional tenses is "cabr-", which is used with the appropriate endings for these tenses.