Of all the mappings that can be defined from the set A : {1,2,3, 4} → B : {5, 6,7 ,8, 9} , a mapping is randomlyselected. The chance that the selected mapping is strictly monotonic is

Each pre-image in set A can be assigned any one of the 5 images from set B Hence total number of functions are n(S)=54=625 For strictly monotonic function either function is increasing or decreasing. For which four different images are used, which can be selected  5C4way. Hence number of monotonic functions are n(A)=2⋅5C4=10 (either increasing or decreasing) ∴ P(A)=10625=2125