Degrees of freedom follow the denominator

Let $X_1,\dots ,X_{12}$ be a random sample from the N(2, 4) distribution and $Y_1,\dots ,Y_{15}$ be a random sample from the N(−2, 5) distribution, where $N(\mu ,{\sigma }^2)$ denotes a normal distribution with mean $\mu$ and variance ${\sigma }^2$. Assume that the two random samples are mutually independent. Let $\bar{X}=(1/12){\sum }_i$₌${}_1^{12}{X}_i,S_1^2=(1/11){\sum }_i$₌${}_1^{12}(X_i-\bar{X}{)}^2$, Ȳ $=(1/15){\sum }_j$₌${}_1^{15}{Y}_j,S_2^2=(1/14){\sum }_j$₌${}_1^{15}(Y_j-$ Ȳ${)}^2$. Which of the following statements are true?