Answer:

Explanation:
mass of the bicycle + cyclist = 50 kg
constant speed = 6 km/h
a cyclist coasting down a 5.0° incline
the downward velocity is constant, so net acceleration must be zero
the air drag must be equal to gravitational force downward along the ramp
now for upward motion





Time = (distance) / (speed)
Time = (4.12x10^16 m) / (3 x10^8 m/s)
Time = 1.37 x 10^8 seconds
Divide the seconds by 86,400 to get days. Then divide the days by 365 to get years.
Time = about 4.35 years