what are koans? In which school are they found? What propuse do they serve?

Kōan is a story, dialogue, question, or statement which is used in Zen practice to provoke the "great doubt" and to practice or test a student's progress in Zen.

Explanation:

the committees of correspondence were the american colonies’ means for maintaining communication lines in the years before the revolutionary war. in 1764, boston formed the earliest committee of correspondence to encourage opposition to britain’s stiffening of customs enforcement and prohibition of american paper money. the following year, new york formed a similar committee to keep the other colonies notified of its actions in resisting the stamp act. in 1773, the virginia house of burgesses proposed that each colonial legislature appoint a committee for intercolonial correspondence. the exchanges that followed built solidarity during the turbulent times and bring about the formation of the first continental congress in 1774.