def find_defined_merchants(rules: list, monthly: dict) -> dict:
    """Helper function to return a dictionary of "relevant" merchants that are defined in the rules list as
    well as merchants defined in the monthly spendings list.

    Args:
        - spendings: dictionary containing total monthly spendings at merchants in a month
        - rules: a list of tupels containg the rules for an amount of rewards points

    Returns:
        - merchants: dictionary of "relevant" merchants for this set of transactions and rules
    """
    merchants = {}
    for rule in rules:
        for merchant in rule[1].keys():
            if merchant in monthly.keys():
                if merchant not in merchants:
                    merchants[merchant] = ""
    return merchants