use python.Write a function named core$\_$temp that takes the core temperature $($in Celsius$)$ of a nuclear reactor and returns the following responses:

'core is shut down' if the temperature is lower than $200$

'core is below optimum' if the temperature is larger or equal than $200$ but smaller than $300$

'core is at optimum' if the temperature is $300$

'core is above optimum' if the temperature is larger than $300$ and smaller than $1800$

'run for your life' if the temperature is larger or equal than $1800$