MHB Number of Onto, Into & Constant Functions from A to B

[juantheron]

If $A = \left\{1,2,3,4,5,6\right\}$ and $B = \left\{a,b,c,d,e\right\}$. Then Total no. of $(1)$ onto function from $A$ to $B$$(2)$ into function from $A$ to $B$$(3)$ Constant function from $A$ to $B$Plz explain it breifly"Thanks"

 

[Plato2]

If $A = \left\{1,2,3,4,5,6\right\}$ and $B = \left\{a,b,c,d,e\right\}$. Then Total no. of
$(1)$ onto function from $A$ to $B$
$(2)$ into function from $A$ to $B$
$(3)$ Constant function from $A$ to $B$

For #1 use inclusion/exclusion to figure the answer.

In #2 how is into used? There are $5^6$ functions from a set six to a set of five.

For #3 think what it means to be a constant function.