7. Consider two components and three types of shocks. A type 1 shock causes component 1 to fail, a type 2 shock causes component 2 to fail, and a type 3 shock causes both components 1 and 2 to fail. The times until shocks 1, 2, and 3 occur are independent exponential random variables with respective rates A1, A2, and A3. Let X, denote the time at which component i fails, / -

1, 2. The random variables X1, X2 are said to have a joint bivariate exponential distribution. Find P(X₁ > 3, X21].