$11-2$ : $($a$)$ Give a polynomial$-$time algorithm that approximates the minimum representative set to within a factor of O$($log n$).$ Specifically, your algorithm should have the following property: If the minimum possible size of a representative set is s$,$ your algorithm should return a representative set of size at most O$($s$$ log n$).($b$)$ Note the close similarity between this problem and the Center Selection Problem$$a problem for which we considered approximation algorithms in Section $11\mathrm{.}2.$ Why doesn$$t the algorithm described there solve the current problem?