4. [20 Points] Write a subroutine that multiplies the top nibble and the bottom nibble of a number in W and returns the result in W. The setup and call of the subroutine are below. Fill in the details between the label Mult_nybbles and the RETURN instruction. Keep your routine less than about 20 instructions, but use any algorithm you like. Hint 1: Split the nybbles into two different registers using ANDWF with a bit mask. Hint 2: keep it simple - remember what you did in grade school. Hint 3: there are more than on solution, if it gets the job done within the about 20 instructions... (feel free to use back of page, but please mark clearly that you have). ; Variable declarations VarA VarB VarC Index EQU H' 20' ; Use these as you wish! EQU H'21' EQU H' 22' EQU H' 23' Constants (for testing) NybbleA EQU H'3' NybbleB EQU H'7' ; Start of code Load_W MOVLW NybbleA Put 0x3 into VarA was MOVWF VarA SWAPF ADDLW VarA, W NybbleB CALL Mult_nybbles MOVWF VarC Mult_nybbles; Write your code below ; Should be NybbleA* NybbleB (0x15) Cero.com