Question

for each permutation of {1, 2, 3, 4, 5, 6, 7}, give the next largest permutation or indicate that the permutation is the last one in lexicographic order.
a. (1,2,3,4,5,6,7)
b, (7,6,5,4,3,2,1)
c. (1,7,6,4,2,3,5)
d. (3,7,6,5,4,2,1)
e. (5,4,7,6,3,2,1)