need help this question

Question 8: Let Time be a partial computable function such that Time((z, x)) is the number of steps required for ?2(x) to return its output, and if ?2(x) , then Time (z, x) 1. [Continued on next page] Prove that Time cannot be extended to a total computable function; i.e. there is no computable function f such that f(x) ? for every nonnegative integer x and f((z, x)) = Time((z, x?) if Time((z, x?) . Hint: Suppose that a total computable function f exists that extends Time. Show how to use f to decide K, the sets {x| xe Wxl.]