Suppose that a patient's pre and post-treatment total cholesterol can be explained by a bivariate normal distribution. If the pre-treatment mean total cholesterol is 250 with a standard deviation of 50 and the mean total cholesterol post-treatment is 225 with standard deviation of 50, and the correlation between the measures is 0.7. What is the probability that for a randomly selected patient the post-treatment total cholesterol will be lower than the pre-treatment level?