The director of studies at a large university would like to advise parents of incoming students about the cost of textbooks during a typical semester. A sample of 100 students indicated an average cost of $315.40 with a standard deviation of $43.20. To test whether the population average is above $300 (using alpha= .05) an appropriate decision rule would be

A. reject Ho if the calculated t > 1.66

B. reject Ho if the calculated t < 1.66

C. do not reject Ho if the calculated t > 1.66

D. reject Ho if the calculated t < - 1.66