A reaction between \(X\) and \(Y\) is studied using initial rates. The data below are obtained at constant temperature. Experiment 1: \([X]=0.10\), \([Y]=0.10\), rate \(=2.0\times 10^{-4}\ \text{mol dm}^{-3}\text{ s}^{-1}\). Experiment 2: \([X]=0.20\), \([Y]=0.10\), rate \(=8.0\times 10^{-4}\). Experiment 3: \([X]=0.10\), \([Y]=0.20\), rate \(=4.0\times 10^{-4}\). What is the rate equation?