Helping my sister with some homework for a year 9 class, but I'm bad at maths too!:(

1) The length of a table is 200cm correct to the nearest cm
What are the upper and lower bounds of the length?

2) A= 4.3 (correct to 2significant figures)
B= 1 correct to 1 significant figure
C= 2.1 correct to 1 decimal place
What is the upper bound of a-c divided by b?

3) when she was born Emily weighed 3kg, correct to the nearest kg. when she was three months old Emily weighed 6kg, correct to the nearest kg. what is the upper bound of the weight she has gained?

4) A case weighs 4kg correct to the nearest kg
Calculate the upper bound of the total weight of 12 of these cases