$4\mathrm{.}2$ KFC has experienced breakdowns with their ovens in the past $18$ months at rates indicated below. Each time an oven breaks down; the restaurant loses an estimated R$40000$ in contingency and service expenses. KFC has an option of purchasing a service contract for preventive maintenance of their oven from the supplier at a price of R$16000$ per month. Even if they purchase preventive maintenance service plan, they will still experience breakdowns, averaging $1$ breakdown per month: $4\mathrm{.}2\mathrm{.}1$ Calculate the monthly breakdown probability based on the past data. $4\mathrm{.}2\mathrm{.}2$ Calculate the expected number of breakdowns per month based on the past data. $4\mathrm{.}2\mathrm{.}3$ Calculate the expected cost of breakdown per month with no preventive maintenance. $4\mathrm{.}2\mathrm{.}4$ Should the company continue with current maintenance policy, or should they outsource preventive maintenance? $($Show all calculations$)$