Faizal 先生住在新加坡东部的一栋排屋里。他正在考虑在家中安装太阳能电池板。他想知道安装太阳能电池板的费用是否能抵消他的电费支出。他做了一些研究，并收到了一家安装太阳能电池板公司的报价。根据他的住宅类型，推荐他使用 60 片电池的太阳能电池板。

1. Identify how many 60-cell panels fit in the more efficient orientation.

For a 60-cell solar panel, the dimensions are approximately $1.0\text{ m} \times 1.65\text{ m}$.

Place the $1.65\text{ m}$ side along the $9\text{ m}$ side of the roof:

$\left\lfloor \frac{9}{1.65} \right\rfloor = 5$

Place the $1.0\text{ m}$ side along the $4\text{ m}$ side of the roof:

$\left\lfloor \frac{4}{1.0} \right\rfloor = 4$

2. Calculate the maximum number of panels and check against the alternative simple orientation.

Number of panels in this arrangement:

$5 \times 4 = 20$

If placed the other way round:

$\left\lfloor \frac{9}{1.0} \right\rfloor \times \left\lfloor \frac{4}{1.65} \right\rfloor = 9 \times 2 = 18$

Hence the maximum number is $20$.