Point $A$ is between towers $B$ and $C.$ The distances of towers $B$ and $C$ from point A are $1000m$ and $2500m$ respectively. Measured from point $A,$ the angle of elevation of the top of $B$ is $19{31}^{\text{'}}$ while angle of elevation of the top of tower $C$ is $.$ The difference in elevations between the top of towers $B$ and $C$ is $75\mathrm{.}3m.$ Considering the effects of curvature and refraction, what is the value of $$ in degrees and minutes? Assume that $B$ is higher than $C.$