In a test of hypothesis, the null hypothesis is that the population mean is equal to 74 and the alternative hypothesis is that the population mean is less than 74. A sample of 20 elements selected from this normal population produced a mean of 68.5 and a standard deviation of 6.4. The significance level is 1%. What is the value of the test statistic, t?a) 6.372
b) -4.076
c) -2.509
d) -3.843
