Q$5(30$ pts$)$ An elevated expressway goes through an urban area and crosses a local street

as shown below. The partial cloverleaf exit ramp is on a $2\%$ downgrade, and all vehicles

leaving the expressway must stop at the intersection with the local street. Determine the

length of the ramp for the following conditions: Maximum speed on expressway $=60mi/$

h; Distance between exit sign and exit ramp $=260ft$; Letter height of road sign $3"$;

Perception$-$ reaction time $2\mathrm{.}5sec$; Expressway grade $0\%.$ Assume that a driver can read a

road sign within his or her area of vision at a distance of $50ft$ for each inch of letter

height, and the driver sees the stop sign immediately on entering the ramp.