Stats question

A chemical plant is allowed to dispose of a certain amount of wastewater into a river. The Environmental Protection Agency (EPA) takes samples of the river water at several locations downstream from the plant. If the plant complies with the EPA regulations, the population mean amount of toxic particles in the water is less or equal to 49 parts per million (ppm). Each day, the EPA selects 38 water samples and computes the average amount of toxic particles, and then uses this information to determine if they should conclude that the population means the amount of toxic particles is greater than 49 ppm. If so, the owner of the plant will be fined. On a random Monday, EPA collected 38 samples and found the mean to be equal to 47 with a standard deviation equal to 9 and a = 0.05. Use 3 decimal places and include the MINUS sign when needed. E.g. -0.123. No credit will be given for rounding mistakes. The test statistic is