The probability that a non-leap year should have $53$ Sundays is ............ (in $/7$)

$1000$ families with $2$ children were selected randomly,and the following data were recorded:

Number of girls in a family	$0$	$1$	$2$
Number of families	$128$	$672$	$200$

Compute the probability of a family,chosen at random,having $(1)$ two girls,$(2)$ one girl.

Can the experimental probability of an event be a negative number? If not,why?

From the list of telephone numbers of $100$ employees of a factory, the following frequency distribution of their unit place digit (for example, in the number $25828573$, the unit place digit is $3$) is given in the table below:

Unit digit	$0$	$1$	$2$	$3$	$4$	$5$	$6$	$7$	$8$	$9$
Frequency	$8$	$9$	$12$	$15$	$10$	$7$	$12$	$10$	$9$	$8$

Find the probability that a randomly selected employee has a telephone number with unit digit $3$.

$80$ bulbs are selected at random from a lot and their lifetime (in $hrs$) is recorded in the form of a frequency table given below:

Lifetime (in hours)	$300$	$500$	$700$	$900$	$1100$
Frequency	$10$	$12$	$23$	$25$	$10$

The probability that a bulb selected randomly from the lot has a lifetime less than $900$ hours is:

The probability of occurrence of event $A$ is $0.43$. The probability of event $A$ not occurring is .........