For positive integers m and n such that m+10<n+1, both the mean and the median of the set {m,m+4,m+10,n+1,n+2,2n} are equal to n. What is m+n?<spanclass=′latex−bold′>(A)</span>20<spanclass=′latex−bold′>(B)</span>21<spanclass=′latex−bold′>(C)</span>22<spanclass=′latex−bold′>(D)</span>23<spanclass=′latex−bold′>(E)</span>24