Show function is primitive recursive

4. Let P(x, t) be a computable predicate, Show f(x, y) be the maximum value of t- y such that P(x,t) = 1. If no such t-y exists with P(x, t) = 1, then f(x,y-0. Show f(x,y) is p.r. 4. Let P(x, t) be a computable predicate, Show f(x, y) be the maximum value of t- y such that P(x,t) = 1. If no such t-y exists with P(x, t) = 1, then f(x,y-0. Show f(x,y) is p.r