Solution (source code)

= Solution
{c}

Comparing the two coefficients in the reciprocal-coordinate transformation gives
$$
\boxed{\alpha=\beta=\frac12.}
$$
The inverse transformation is $h_r=h_p+k_p$, $k_r=k_p-h_p$. This provides an independent check on the signs associated with the two primitive arrows in the source.