In the xy-plane, the graph of a linear equation of the form y = mx + b and the graph of an exponential equation of the form y = abx both contain points (1, 3) and (2, 4). If the point (r, s) is on the graph of the linear equation and the point (r, t) is on the graph of the exponential equation, where 0 < r < 4 and s > t, which of the following must be true?