Given real vectors v and r of the same size, what are the following, and how are they duals? 
 1. inf{v'*inv(R)*v : R>0, diag(R)= r}
 2. sup{v'*R*v      : R>0, diag(R)= r}
Note: R > 0 denotes positive definiteness, x' denotes transpose, and inf, and sup are the infimum and supremum.