Explanation

For a GARCH(1,1) process to be stable, the parameters must satisfy the following conditions:

1. All parameters (α, β, γ) must be positive
2. The sum of α + β + γ must equal 1
3. The sum of α + β must be less than 1 (since γ = 1 - α - β > 0)

Let's verify each option:

Option A: α = 0.073637, β = 0.927363
Sum = 0.073637 + 0.927363 = 1.001000 > 1
❌ Not stable (sum > 1)

Option B: α = 0.075637, β = 0.923363
Sum = 0.075637 + 0.923363 = 0.999000 < 1
γ = 1 - 0.999000 = 0.001000 > 0
✅ Stable (sum < 1, γ > 0)

Option C: α = 0.084637, β = 0.916363
Sum = 0.084637 + 0.916363 = 1.001000 > 1
❌ Not stable (sum > 1)

Option D: α = 0.086637, β = 0.914363
Sum = 0.086637 + 0.914363 = 1.001000 > 1
❌ Not stable (sum > 1)

Only Option B satisfies the stability condition where α + β < 1, ensuring that γ = 1 - α - β > 0, and all parameters are positive.