Let X1, X2, and X3 represent the times necessary to perform…

Let X1, X2, and X3 represent the times necessary to perform three successive repair tasks at a certain service facility. Suppose that each are independent normally distributed random variables with expected values µ1 = µ2 = µ3  = 65 and variances σ_1^2= σ_2^2=σ_3^2=20 respectively. What is the value of E[2X1+X2-X3]? _______

A pediatrician wishes to recruit 5 couples who are expecting…

A pediatrician wishes to recruit 5 couples who are expecting their first child to participate in a new natural childbirth regimen. Let p = 0.20 be the probability that any one couple agrees to participate. What is the probability that exactly 15 couples must be approached before 5 couples agree to participate? _______