(5 points) Fix any positive integer n and consider the trace operator: Tr : Roxn - R. The trace operator sums up the diagonal entries of a matrix. In other words, if A c Roxx and the entry in the ith row and jth column is a;;, then Tr(A) = _ _, qu. Note that the trace operator is a linear operator. Define the inner product on Roxx as (A, B) = Zij_1 aajbij. (Here, similarly to above, bij refers to the entry in the ith row and jth column.) Define the inner product on R as simply (r, y) = ry. What is the adjoint of Tr(.)