Multiply. \( \begin{array}{l}\left(a^{2}+a-1\right)\left(a^{2}+6 a-8\right) \\ \\ \left(a^{2}+a-1\right)\left(a^{2}+6 a-8\right)=\square \\ \text { (Simplify your answer.) }\end{array} \)

Calculate or simplify the expression \( (a^2+a-1)(a^2+6a-8) \). Simplify the expression by following steps: - step0: Solution: \(\left(a^{2}+a-1\right)\left(a^{2}+6a-8\right)\) - step1: Apply the distributive property: \(a^{2}\times a^{2}+a^{2}\times 6a-a^{2}\times 8+a\times a^{2}+a\times 6a-a\times 8-a^{2}-6a-\left(-8\right)\) - step2: Multiply the terms: \(a^{4}+6a^{3}-8a^{2}+a^{3}+6a^{2}-8a-a^{2}-6a-\left(-8\right)\) - step3: Remove the parentheses: \(a^{4}+6a^{3}-8a^{2}+a^{3}+6a^{2}-8a-a^{2}-6a+8\) - step4: Add the terms: \(a^{4}+7a^{3}-3a^{2}-14a+8\) The product of \( (a^{2}+a-1) \) and \( (a^{2}+6a-8) \) is \( a^{4}+7a^{3}-3a^{2}-14a+8 \).