A certain species of East Anglian goblin has left arm of mean length 100cm with standard deviation 1cm, and right arm of mean length 102cm with standard deviation 2cm. The correlation of left- and right-arm-length of a goblin is 1 2. You may assume that the distribution of left- and right-arm-lengths can be modelled by a bivariate normal distribution. What is the probability that a randomly selected goblin has longer right arm than left arm