With reference to the statement made on page 14 of his department's Annual Operational Plan for the 2015-16 financial year that the Public Service continues to face substantial challenges around recruiting competent senior managers and developing them to be able to carry out the mandate of Government effectively, what are the details of (a) the challenges, including (i) the departments affected, (ii) the magnitude of the challenges, (iii) the (aa) vacancy and (bb) turnover rate of senior managers per department, and (iv) the identified impact on service delivery, and (b) the measures (i) in place or (ii) planned to address the challenges?