目的是设计一个函数,以计算价格与给定的税率折扣后的总额.
给出一个字符串s和一个整数k,从字符串开始计算的每2k字符,反转第一个k字符.如果剩下的字符少于k字符,反转所有.如果有2k字符,但小于或等于k字符,则反转第一个k字符,而另一个字符则保留原始.
To implement the given string problem in Python, you can use slicing and string concatenation. Here is the code:

```
def reverse_string(s, k):
    result = ""
    i = 0
    while i < len(s):
        # reverse first k characters
        if i + k <= len(s):
            result += s[i:i+k][::-1]
            i += k
        # reverse remaining characters
        else:
            result += s[i:][::-1]
            break
        # leave next k characters as original
        if i + k <= len(s):
            result += s[i:i+k]
            i += k
        # include remaining characters as is
        else:
            result += s[i:]
            break
    return result
```

To calculate the total amount after discounting the price with the given tax rate, you can use the following formula:

```
total_amount = price - price * (tax_rate / 100)
```

Here, `price` is the original price and `tax_rate` is the percentage of tax to be applied.