Pooled Regression

Two separate datasets are used to fit simple ordinary least squares regressions through the origin. For the first dataset, the sum of the squared predictor values is $120$ and the fitted coefficient is $1.5$. For the second dataset, the sum of the squared predictor values is $80$ and the fitted coefficient is $3$. The datasets are then combined, and one ordinary least squares regression through the origin is fitted to every observation. What is the coefficient of the combined regression?