Answer:
(B) Mean 3 and standard deviation 5
Step-by-step explanation:
Property of mean
The mean of the sum or difference of two random variable R and S is the sum of their means.
μ (R-S) = μ(R) - μ(S)
μ(R-S) = 10 - 7 = 3
Property of standard deviation
The variance of Independent variable R and S is is the sum of their variances. Even when we subtract two random variables, we still add their variances; subtracting two variables increases the overall variability in the outcomes.
σ^2(R-S) = σ^2 (R) + σ^2(S)
= 16 + 9 ( variance = (standard deviation)^2 )
= 25
σ(R-S) = 5
