An application of exponential sum estimates

Let p be an odd prime and let delta be a fixed real number with 0 < delta < 2. For an integer a with 0 < a < p, denote by (a) over bar the unique integer between 0 and p satisfying as a (a) over bar equivalent to 1 (mod p). Further, let {x} denote the fractional part of x. We derive an asymptotic formula for the number of pairs of integers (a,b)with 1 less than or equal to a less than or equal to p-1,1 less than or equal to b less than or equal to p-1, \{a(k)/p}+{b(k)/p}-{a(-1)/p}-{b(-1)/p}\< delta.