An ANOVA procedure is applied to data obtained from four distinct populations. The samples, each comprised of 15 observations, were taken from the four populations. The degrees of freedom for the numerator and denominator for the critical value of F are:___________
a. 3 and 56, respectively.
b. 3 and 59, respectively.
c. 4 and 21, respectively.
d. 4 and 60, respectively