In November 2018, Mr. N, a notorious criminal, was found guilty of three (3) counts of Murder and was consequently sentenced with the penalty of reclusion perpetua for each count. A month after, he was likewise found guilty of five (5) counts of Grave Threats in a separate criminal proceeding, and hence, meted with the penalty of prision mayor for each count. How long will Mr. N serve all his penalties of imprisonment? Explain. (2019 BAR)