1) Sample space = (MNS, MSN, MMS, MMN, MNN, MSS, SMN, SNM, SSM, SSN, SMM, SNN, NMS, NSM, NNS, NNM, NMM, NSS, MMM, SSS, NNN) All you need to do is write down all the possible combinations of the 3 letters together.
2) Charlie is correct.
3) Notice how there are only mystery, non-fiction, and science books in the bag, There are no magazines in the bag, so there is a 0% chance he selects one.
Hope this helps!