Assume the PC station is $12+25\mathrm{.}32ft.,$ the degree of curvature is $10$ degrees, and the length of curve is

$638\mathrm{.}90$ ft $.$

You are occupying station $14+25\mathrm{.}32,$ backsighting the PC$,$ flopping your scope, zeroing the horizontal

circle, and measuring clockwise horizontal angle to station $16+25\mathrm{.}32.$ This deflection angle is

$($a$)10$ deg $.$

$($b$)20$ deg $.$

$($c$)30$ deg $.$

$($d$)40$ deg $.$