A restaurant claims that each of their burgers has a 1/4 pound of meat after it is prepared. Of course this is not exact. The students in a local high school measured some of these burgers for a science project, and they concluded that the expected weight of such a burger is 0.251 pounds, but the standard deviation is 0.02 pounds. Afterwards, the 30 students celebrate by each ordering 1 burger. What is the probability that, among the 30 students, the average weight of a burger is less than the advertised weight of 1/4 pound?