```/* nag_monotonic_intg (e01bhc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.1, 2017.
*/

#include <nag.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nage01.h>

int main(void)
{
Integer exit_status = 0, n, r;
NagError fail;
double a, b, *d = 0, *f = 0, integral, *x = 0;

INIT_FAIL(fail);

printf("nag_monotonic_intg (e01bhc) Example Program Results\n");
scanf("%*[^\n]"); /* Skip heading in data file */
scanf("%" NAG_IFMT "", &n);
if (n >= 2) {
if (!(d = NAG_ALLOC(n, double)) ||
!(f = NAG_ALLOC(n, double)) || !(x = NAG_ALLOC(n, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
}
else {
printf("Invalid n.\n");
exit_status = 1;
return exit_status;
}
for (r = 0; r < n; r++)
scanf("%lf%lf%lf", &x[r], &f[r], &d[r]);
printf("                                          Integral\n");
printf("          a                  b            over (a,b)\n");
/* Read a, b pairs until end of file and compute
* definite integrals.
*/
while (scanf("%lf%lf", &a, &b) != EOF)
{
/* nag_monotonic_intg (e01bhc).
* Evaluation of interpolant computed by
* nag_monotonic_interpolant (e01bec), definite integral
*/
nag_monotonic_intg(n, x, f, d, a, b, &integral, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_monotonic_intg (e01bhc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
printf("%13.4f      %13.4f      %13.4f\n", a, b, integral);
}
END:
NAG_FREE(d);
NAG_FREE(f);
NAG_FREE(x);
return exit_status;
}
```