A property-price model is trained on four homes. The raw features are:
| home | bedrooms | age (years) |
|---|---|---|
| A | 2 | 10 |
| B | 3 | 5 |
| C | 3 | 20 |
| D | 4 | 8 |
Before fitting, a column of ones is prepended to this table so the model can learn an intercept. Call the resulting design matrix , with its columns ordered .
What is the shape of , and what is the value of its diagonal entry belonging to the bedrooms column?
Select all that apply.