A missile launch code has been shared among 20 officers using a secret-sharing scheme, such that the code can be recovered iff at least 5 officers...

A missile launch code has been shared among 20 officers using a secret-sharingscheme, such that the code can be recovered iff at least 5 officers combine their shares.You are not one of the officers. Each day you have a meeting with a uniformly randomofficer (independently of other days). If you have not previously met with that officer,then you bribe him to get his share of the secret. In expectation, how many days doesit take before you can recover the secret? Give an exact expression and show your work.