We will calculate the total surface area;
The total surface area is given by
![\text{TSA}=a(a+\sqrt[]{a^2+4h^2})](https://img.qammunity.org/2023/formulas/mathematics/college/u6sedet65vrt1u4wtetb8oonqlvpinlv5n.png)
where a is the base-length and h is the height
From the fig.
a=6cm
h=15cm
substituting into the formula;
![\text{TSA}=6(6+\sqrt[]{6^2+4(15)^2})](https://img.qammunity.org/2023/formulas/mathematics/college/8w8xkxl5gr2ma3jetshpoolsu9bqzao6du.png)
Then evaluate;
![\text{TSA}=6(6+\sqrt[]{36+900}](https://img.qammunity.org/2023/formulas/mathematics/college/azlz64l2g6mkitx2kpk55akssoc8c9yhu7.png)
![=6(6+\sqrt[]{936)}](https://img.qammunity.org/2023/formulas/mathematics/college/nm0m4ke8qp0kiaqg267y01u7zmunhmpx2g.png)

=6(36.6)
=219.6 cm²
A gold foil of area 219.6 cm² is needed