function [A,b] = steamSystem(p,T,h)
% steamSystem  System of equations to obtain an interpolant of the steam table
%              The interpolant is of the form
%
%                    h = c_1 + c_2 * p + c_3 * T + c_4 * p * T
%
%              where h is the enthalpy, p is the pressure, and T is the
%              temperature
%
% Synopsis:  [A,b] = steamSystem(p,t,h)
%
% Input:     p,T,h = vectors containing known pressure, temperature and
%                    enthalpy values.  The p, T and h vectors can be
%                    row or column vectors so long as they all have the
%                    same number of elements
%
% Output:    A, b = matrix and right hand side vector that define the system
%                   of equations for the interpolant as A*c = h where c is
%                   the four-element column vector of coefficients for the
%                   interpolant.

A = [ones(size(p(:)))  p(:)  T(:)  p(:).*T(:)];
b = h(:);