What is the unit for surface area?

The value of E(X) is 1.56

Step-by-step explanation:

Number of Boxes=4

Number of Balls =3

If X is the number of box in which the balls are than the number of balls in the box are given as ((4-X)+1)^3

Number of ways such that all the balls are in the box number 4, no balls in the first three boxes is given as n(x=4)=1^3=1

Number of ways such that all the balls are in the box number 3,  is given as n(x=3)=n(x=2)-n(x=4)=2^3-1^3=7

Number of ways such that all the balls are in the box number 2,  is given as n(x=2)=n(x=1)-n(x=3)=3^3-2^3=19

Number of ways such that all the balls are in the box number 1,  is given as n(x=1)=n(x=4)-n(x=3)=4^3-3^3=37

So the total number of ways are

n(total)=n(x=4)+n(x=3)+n(x=2)+n(x=1)

n(total)=1+7+19+37=64

So Probabilities are given as

p(x=1)=n(x=1)/n(total)=37/64

p(x=2)=n(x=2)/n(total)=19/64

p(x=3)=n(x=3)/n(total)=7/64

p(x=4)=n(x=4)/n(total)=1/64

So the E(x) is given as

So the value of E(X) is 1.56