HTML Charges Calculation [closed]

I have the following code to do charges calculation.

Strictly confidential external

Rajitha Lakmal
to Rajitha
4 hours agoDetails
<!DOCTYPE html>
<html>
<head>
    <title>Loan Calculator</title>
</head>
<body>
    <h1>Loan Calculator</h1>
    <label for="loan-type">Select loan type:</label>
    <select id="loan-type">
        <option value="primary-commercial">Primary Mortgage - Commercial Loans</option>
        <option value="additional-commercial">Additional Mortgage - Commercial Loans</option>
        <option value="nivahana-housing">Primary and Additional Mortgages - Nivahana Housing Loans</option>
    </select>
    <br><br>
    <label for="loan-amount">Loan amount:</label>
    <input type="number" id="loan-amount">
    <br><br>
    <button onclick="calculateLoan()">Calculate</button>
    <br><br>
    <p id="result"></p>
    <script>
        function calculateLoan() {
            let loanType = document.getElementById("loan-type").value;
            let loanAmount = document.getElementById("loan-amount").value;
            let result = document.getElementById("result");
            if (loanType === "primary-commercial") {
                if (loanAmount < 1000000) {
                    result.innerHTML = "Total payment: " + (loanAmount * 0.01);
                } else if (loanAmount < 25000000) {
                    result.innerHTML = "Total payment: " + ((loanAmount - 1000000) * 0.0075 + 10000);
                } else if (loanAmount < 50000000) {
                    result.innerHTML = "Total payment: " + ((loanAmount - 25000000) * 0.006 + 190000);
                } else if (loanAmount < 75000000) {
                    result.innerHTML = "Total payment: " + ((loanAmount - 50000000) * 0.006 + 340000);
                } else if (loanAmount < 100000000) {
                    result.innerHTML = "Total payment: " + ((loanAmount - 75000000) * 0.005 + 465000);
                } else {
                    result.innerHTML = "Total payment: " + ((loanAmount - 100000000) * 0.001 + 527500);
                }
            } else if (loanType === "additional-commercial") {
                if (loanAmount < 25000000) {
                    result.innerHTML = "Total payment: " + (loanAmount * 0.004);
                } else if (loanAmount < 50000000) {
                    result.innerHTML = "Total payment: " + ((loanAmount - 25000000) * 0.0025 + 100000);
                } else if (loanAmount < 100000000) {
                    result.innerHTML = "Total payment: " + ((loanAmount - 50000000) * 0.0015 + 162500);
                } else {
                    result.innerHTML = "Total payment: " + ((loanAmount - 100000000) * 0.00075 + 237500);
                }
            } else if (loanType === "nivahana-housing") {
                if (loanAmount < 25000000) {
                    result.innerHTML = "Total payment: " + (loanAmount * 0.0075);
                } else {
                    result.innerHTML = "Total payment: " + ((loanAmount - 25000000) * 0.0025 + 187500);
                }
            }
        }
    </script>
</body>
</html

I want to Add ” Declaration Charge – Rs. 1000.00 and get a sub total.

After sub total Add 2.56% as a Tax. After get total add 15% from that amount. And get total.