How many half adders are required to realize the following $4$ functions? $f_1=A\oplus B\oplus C$ $f_2=\overline{A}BC+A\overline{B}C$ $f_3=AB\overline{C}+(\overline{A}+\overline{B})C$ $f_4=ABC$

It is necessary to design a decimal Adder for two digits represented in Excess-3 code. Show that the correction after adding the two digits with a four-bit binary adder is as follows. The output carry is equal to the carry from the binary adder. If the Output carry is 1 ... add 0011. if the output carry is 0 then add 1101. construct a four-bit decimal adder using two 4-bit adders and an inverter..