ANSWER
1001
EXPLANATION
The sum of the first n - natural numbers is

The sum of the first 1000 terms is



The sum of the first 1001 terms is



The difference is

This is the concept of probability, we are required to calculate for the probability of rolling a 4 with a single die four times in a row;
To solve this we proceed as follows;
The probability space of a die is x={1,2,3,4,5,6}
The probability of a die falling on any of this number is:
P(x)=1/6
Thus the probability of rolling a 4 with a single die four times which makes up mutually exclusive events will be:
1/6*1/6*1/6*1/6
=(1/6)^4
=1/1296
The answer is B] 1/1296
24+26=48 The mother is 48 years old