(1) The unit’s place digit of 129121+ 7867 = Unit’s place digit of129121+ Unit’s place digit of 78^67 = Unit’splace digit of9121 + Unit’s placedigit of 867 = Unit’s place digit of 91 + Unit’splace digit of 83 (since the order ofcycles of 9 and 8 are 2 and4, respectively)= Unit’s place digit of (9 + 2) = 1