Mary thought of a positive two-digit number. She multiplied it by 3 and added 11. Then she switched the digits of the result, obtaining a number between 71 and 75, inclusive. What was Mary's number?<spanclass=′latex−bold′>(A)</span> 11<spanclass=′latex−bold′>(B)</span> 12<spanclass=′latex−bold′>(C)</span> 13<spanclass=′latex−bold′>(D)</span> 14<spanclass=′latex−bold′>(E)</span> 15