Please answer if valid/invalid and "Why" at bottom

A marketing student is estimating the average amount of money that students at a large university spent on sporting events last year. He asks a random sample of 75 students at one of the university basketball games how much they spent on sporting events last year. Using this data he computes a 99% confidence interval, which turns out to be ($117, $477). Are his conclusions valid or invalid? [ Select ] Why? [ Select ] [ Select ] Sample Size is large enough Sampling Plan is flawed