You are a helpful assistant that can solve the given question step by step with the help of the wikipedia search tool and python interpreter tool. Given a question, you need to first think about the reasoning process in the mind and then provide the answer. During thinking, you can invoke the wikipedia search tool to search and python interpreter tool to calculate the math problem for fact information about specific topics if needed. The reasoning process and answer are enclosed within <think> </think> and <answer> </answer> tags respectively, and the search query and result are enclosed within <search> </search> and <result> </result> tags respectively. For example, <think> This is the reasoning process. </think> <search> search query here </search> <result> search result here </result> <think> This is the reasoning process. </think> <python> python code here </python> <result> python interpreter result here </result> <think> This is the reasoning process. </think> <answer> The final answer is \[ oxed{answer here} \] </answer>. In the last part of the answer, the final exact answer is enclosed within oxed{} with latex format.
system
a) In Mexico City, there are regulations that restrict private cars from driving on city streets on two specified days of the week. A family needs to have at least ten cars available every day. What is the minimum number of cars the family needs if they can choose the restricted days for their cars?

b) In Mexico City, each private car is restricted from driving on city streets on one specified day of the week. A wealthy family of ten people has bribed the police, allowing them to suggest two days, from which the police choose one as the restricted day. What is the minimum number of cars the family needs to buy to ensure that each family member can drive every day, given that the assignment of restricted days is done sequentially?
user
12
rule
a) In Mexico City, there are regulations that restrict private cars from driving on city streets on two specified days of the week. A family needs to have at least ten cars available every day. What is the minimum number of cars the family needs if they can choose the restricted days for their cars?

b) In Mexico City, each private car is restricted from driving on city streets on one specified day of the week. A wealthy family of ten people has bribed the police, allowing them to suggest two days, from which the police choose one as the restricted day. What is the minimum number of cars the family needs to buy to ensure that each family member can drive every day, given that the assignment of restricted days is done sequentially?
train