Complete the table series riddle by finding the number that can replace "??".

Count the number of balls in picture below:

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

You walk into a creepy house by yourself. There is no electricity, plumbing, or ventilation. Inside you notice 3 doors with numbers on them. Once you open the doors you will die a particular way. Door No.1 You’ll be eaten by a lion who is hungry. Door No.2 You’ll be stabbed to death. Door No.3 There is an electric chair waiting for you. Which door do you pick?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

You have 10 balls with you. A friend of yours out of nowhere asks you to place those ten balls in five lines such that each of the lines has exactly 4 balls on them. He needs to check your intelligence. Prove him by doing the task.

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

What does this rebus means ?

PROG WORKRESS

I am white when I am dirty, and black when I am clean. What am I?

No matter how little or how much you use me, you change me every month. What am I?