engineering problematics

Charles stays on the 17th floor and he wants to go to the first floor. There are 2 lifts that services his HDB flat. Lift A is at the 3rd floor and lift B is at the 15th floor. When he presses the button to summon the lifts. Lift A moves from the 3rd floor towards the 17th floor. After lift A past the 16th floor, lift B begin moving from the 15th floor to the 17th floor too. Both lift A and lift B arrive at the the 17th floor one second after another. Charles wonder why couldn't lift B have been sent to the 17th floor to pick him up without activating lift A from the 3rd floor. a) Deduce the logical algorithm used to control the lifts b) Write a new decision algorithm to optimize the system. Minimizing the distance traveled by the lifts and waiting time of the residents. (Hint: Make use of that you have learn in electrical engineering applications to solve real life problems.)

I would gladly do it for a fee.