Mark is using a one-sample t-test on the following group: Subject #15: 7.5 hours Subject #27: 6 hours Subject #48: 7 hours Subject #80: 6.5 hours Subject #91: 6.5 hours Subject #59: 7 hours Select the two TRUE statements. a.) The value for the degrees of freedom for Mark's sample population is six. b.) The t-distribution that Mark uses has thinner tails than a standard distribution. 0 c.) The value for the degrees of freedom for Mark's sample population is five. d.) Mark would use the population 0 standard deviation to calculate