a) i got {5,7,10,15,21} therefore it's 5, but the answer is {7,10,15,21} so it's 4.22,5,7,2,23,10,15,21,3,17

a) What is the increasing subsequence of maximal length ?

b) what is the decreasing subsequence of maximal length?

b) {22,10,3} therefore it's 3?

Please help me