How many positive integers n are there such that 3n2+3n+7 is a perfect cube?<spanclass=′latex−bold′>a)</span>0<spanclass=′latex−bold′>b)</span>1<spanclass=′latex−bold′>c)</span>3<spanclass=′latex−bold′>d)</span>7<spanclass=′latex−bold′>e)</span>Infinitely many