A ramp is to be constructed from the ground up to the entrance of a platform that is 1.5 m high. The angle that the ramp makes with the ground satisfies cosϕ=21.
a. (i) Determine the acute angle ϕ that the ramp makes with the ground.
b. (ii) Using the angle obtained in part (i), calculate the length of the ramp required to reach the platform.
c. (iii) If safety regulations require the ramp to be at least 4 m long, state whether the planned ramp meets the requirement and justify your answer with calculation.