P. 4196. A hard sheet making an angle of 45o with the horizontal is placed below a falling marble. The marble falls from a height of 2 metres and collides totally elastically with the hard sheet. Where must the sheet be placed in order to make
a) the horizontal distance covered by the marble until it hits the ground the greatest;
b) the time until the marble hits the ground the greatest?
Deadline expired on 10 December 2009.