John makes random guesses on his multiple-choice test, which has five options for each question. Let the random variableXbe the number of guesses taken beforeguessingcorrectly.

Assuming theguesses are independent, find the probability that he doesn't guess correctly until his 6thguess.

a) 0.3277

b) 0.3521

c) 0.0789

d) 0.0655