How can I do the math specifically on this

The water rates vary depending on the type of usage. A code of H means home use, a code of C means commercial use, and a code of I means industrial use. Any other code value should be treated as an error. Water rates are computed as follows:
Code H: Code C:
Code I:
$5.00 plus $0.005 per gallon
$1000.00 for the first 4 million gallons used plus
$0.025 for each additional gallon used
$1000.00 if usage does not exceed 4 million gallons
$2000.00 is usage is between 4 million and 10 million gallons $3000.00 is 10 million gallons or more

To do the math specific to the water rates, you need to identify the type of usage based on the given code and then use the appropriate formula to calculate the cost. Here's how to do it:

1. Start by checking the code value:
- If the code is H, it represents home use.
- If the code is C, it represents commercial use.
- If the code is I, it represents industrial use.
- If the code is anything other than H, C, or I, it should be considered an error.

2. If the code is H, use the following formula to calculate the cost:
Cost = $5.00 + ($0.005 per gallon) * (number of gallons used)

3. If the code is C, use the following formula to calculate the cost:
- If the usage does not exceed 4 million gallons:
Cost = $1000.00
- If the usage is between 4 million and 10 million gallons:
Cost = $2000.00
- If the usage is 10 million gallons or more:
Cost = $3000.00
- For any additional gallons used:
Cost += ($0.025 per gallon) * (number of additional gallons used)

4. If the code is I, use the following formula to calculate the cost:
Cost = $1000.00 for the first 4 million gallons used
Cost += ($0.025 per gallon) * (number of additional gallons used)

Remember to substitute the actual number of gallons used into the formula to calculate the cost accurately.