E[R] below can be computed depending on the random process... Try to guess what it is before computing. Randomness may be a fancy business...
See a similar concept: Bertrand Paradox
Dervish Fox: How can you cut a square randomly?
Red Fox: Here is a way; first generate a random number to represent point A. Then another random number for point B along the three others sides. Drawn the line AB, and cut it out.
Dervish: And how can you generate a random number?
Red: Excel does it easily. Type "=RAND()", and boom, you get one right away.
Dervish: But that depends on some seed numbers in the machine's memory, no?
Red: Yes, that's why they call them pseudo-random numbers. Do you have a problem with that?
Dervish: I have a bigger problem than that.
Red: So... you believe that random numbers can't exist.
Dervish: I believe that the word "random" should be removed from all world dictionaries.
Red: Radical.

Dervish Fox: How can you cut a square randomly?
Red Fox: Here is a way; first generate a random number to represent point A. Then another random number for point B along the three others sides. Drawn the line AB, and cut it out.
Dervish: And how can you generate a random number?
Red: Excel does it easily. Type "=RAND()", and boom, you get one right away.
Dervish: But that depends on some seed numbers in the machine's memory, no?
Red: Yes, that's why they call them pseudo-random numbers. Do you have a problem with that?
Dervish: I have a bigger problem than that.
Red: So... you believe that random numbers can't exist.
Dervish: I believe that the word "random" should be removed from all world dictionaries.
Red: Radical.