Vimala was asked to simplify the expression \(2y(5y^{3} - 5y + 9)\).
She wrote the result as \(10y^{3} - 10y + 18y\)
However, her teacher marked her answer incorrect.
Based on the situation, answer the following questions.
1. What should be the correct expansion of \(2y(5y^{3} - 5y + 9)\)?
2. What error did Nilan make while multiplying the expressions?
3. Which rule of exponents should he use to rectify his mistake?
4. What is the degree of the correct expansion?