Pobability pmf of 1 thing is greater than another* help needed*

[cloud360]

Pobability pmf of 1 thing is greater than another*urgent help needed*

Homework Statement

In the game of Risk, battles are decided by the rolling of dice. Suppose that there are two armies,
red and blue. The red army rolls three dice and the blue army rolls two dice. Whichever army rolls
the highest number (on a single die) is declared the winner. In the event of a tie (both armies have
the same highest number), the blue army is declared the winner.

(c) Calculate the probability that the red army wins.

Homework Equations

cdf=cumulative distribution function=p(x<=X)

The Attempt at a Solution

I don't know how to do last question. But i have this info to answer it.i collected this info by answering question 1 + 2 which i have not included here.


[PLAIN]http://img233.imageshack.us/img233/8079/pmfdf.gif

 

[cloud360]

anyone

 

[cloud360]

i think we let x=k

pmf a> pmf b

let pmf a = p(x=k)
pmf b=p(x=k-1)

then pmf a * pmf b = p(x=k)*p(x=k-1).....is this correct