The chart shown gives the cost of installing carpet in four rectangular rooms of various sizes. The cost per square metre of installing carpet is always the same.

Width (metres)

Length (metres)

|  | 10 | $y$ |
| :---: | :---: | :---: |
| 15 | $\$ 397.50$ | $\$ 675.75$ |
| $x$ | $\$ 742.00$ | $\$ z$ |

What is the value of $z$ ?
(A) 331.25
(B) 463.75
(C) 1815.25
(D) 476.00
(E) 1261.40