A wire is made from a $3.0\,\text{m}$ section of metal X connected to a $1.0\,\text{m}$ section of metal Y, and its cross-sectional area is constant throughout. When a load is suspended from the wire, metal X increases in length by $1.5\,\text{mm}$ and metal Y increases in length by $1.0\,\text{mm}$. Next, the same load is suspended from a second wire with the same cross-sectional area, but this one contains $1.0\,\text{m}$ of metal X and $3.0\,\text{m}$ of metal Y. What is the overall extension of this second wire?
- A$2.5\,\text{mm}$
- B$3.5\,\text{mm}$
- C$4.8\,\text{mm}$
- D$5.0\,\text{mm}$