There are three alloys $\mathrm { A } , \mathrm { B }$ and C that contain, among other metals, gold and silver in the proportions indicated in the attached table.
| Gold (\%) | Silver (\%) |
| A | 100 | 0 |
| B | 75 | 15 |
| C | 60 | 22 |
It is desired to obtain an ingot of 25 grams, with a proportion of $72 \%$ gold and a proportion of $16 \%$ silver, taking $x$ grams of $\mathrm { A } , y$ grams of B and $z$ grams of C . Determine the quantities $x$, $y , z$.