The ratio (U/10)/(V/15) of two independent Xo) and xs) variables, U and V respectively, should give: a. X25) distribution. b. t-Distribution with 25 degrees of freedom. c. F-Distribution with 10, and 15 degrees of freedoms respectively. The mean and variance of 10) distribution should be: a. Mean is 10, Variance is 10 b. Mean is 10, Variance is 20 c. Mean is 20, Variance is 10