Problem $2$: A horizontal curve on a single$-$lane freeway ramp is $400$ ft long, and the design speed of the ramp is $45$ mi$/$h$.$ If the superelevation is $10\%$ and the station of the PC is $18+25,$ determine:

a$.$ the curve radius

b$.$ the central angle

c$.$ the tangent length

d$.$ the station of the PI

e$.$ the station of the PT

f$.$ the stopping sight distance

g$.$ the distance that needs to be cleared from the center of the lane to provide adequate stopping sight distance