4. Using finite summation notation, write a general formula for a binary integer, B, in 2's complement with b number of bits 5. Sign extension means that any given signed number can be represented with more bits by simply repeating the sign bit. For example, 0005 = +5 and 00005 = +5. This holds true for negative numbers as well. For example, 10115 and 11011-5. Also, 11111011-5. Using finite summation notation, prove that sign extension can be applied to any 2's complement binary integer, B, with b number of bits