Problem $4$: $($Note: Save your code in module $$ModuleProblem$4)$

$1.$ Write a function $$MyFunction$$ which takes as input a range and an integer which

returns:

a$.$ The sum of the range if the integer argument value is $1$

b$.$ The sum of squares of the range if the integer argument value is $2$

c$.$ The average of the range if the integer argument value is $3$

d$.$ Nothing if the integer argument value is anything else

$2.$ Use VBA to place the function from part $1$ in cell C$1$ on the worksheet A$.$ First use input

boxes to take the input arguments. $($Set the default value of the range argument to

a$1$:a$20).$ A command button that calls this sub should be placed on worksheet A$.$

Hint: Use the $.$formula property

$3.$ Write a sub which appends a random number $($between $1$ and $4$ inclusive$)$ of cells with a

random value $($between $1$ and $20$ inclusive$)$ to the end of the list of numbers in column A$.$

$4.$ When the workbook is opened:

a$.$ Select worksheet B

b$.$ Call the sub from part $3$