After rounding the final turn in the bell lap, two runners emerge ahead of the pack. When Runner $A$ is 200 ft from the finish line, his speed is $22 \mathrm{ft} / \mathrm{sec}$, a speed that he maintains until he crosses the line. At that instant of time, Runner $B$, who is $20 \mathrm{ft}$ behind Runner $A$ and running at a speed of $20 \mathrm{ft} / \mathrm{sec}$, begins to sprint. Assuming that Runner $B$ sprints with a constant acceleration, what minimum acceleration will enable him to cross the finish line ahead of Runner $A$ ?