4-2+signification++figures

How many significant figures in the following numbers?
 * 1) 3423.34=6
 * 2) 2304.3=5
 * 3) 2050=3
 * 4) .0342=3
 * 5) 3434.34340= 9
 * 6) 4=1
 * 7) 400=1
 * 8) .4=1
 * 9) .40=2
 * 10) .400=3
 * 11) 10000000000=1
 * 12) 1=1
 * 13) 1.00=3
 * 14) 304050607=9
 * 15) 99=2
 * 16) number of doors in this room=2
 * 17) number of glass cabinets in this room=22
 * 18) number of drawers in this room=32
 * 19) number of chairs and stools in this room=32
 * 20) number of people cooler than Mr. Bair (hint the answer is zero, but not according to his wife =)) a million people are cooler then mr. bair