Need to modify script to avoid API call

I have the following script in a Rollbase page. It selects a VAT rate based on a VAT code in the page and calculates the VAT Amount. However we get a message about exceeding API calls (limit being 1000) after just a dozen or so calculations.

In order to get round this for now I want to just hard-code the VAT Rate (20%) in the script and not perform any API calls  - which I am assuming is the "Select  vat_rate etc..."

So I think I want vatDec to be assigned a value of 20.

However whatever modifications I try I cannot get it to work.

I would be grateful for pointers as to what modification would work. Thanks. Richard.

function computePrice() {
    var goods   = rbf_getFieldValue("goods");
    var taxCode = rbf_getFieldValue("vat_cd");


    rbf_selectValue("SELECT vat_rate FROM vat_rate WHERE vat_code='"+taxCode+"'", function(vatDec) {
        var vatAmt = parseFloat(goods.substring(1)) * (parseFloat(vatDec) / 100);

         
                var total = parseFloat(goods.substring(1)) + vatAmt;
        rbf_setFieldValue("vat", vatAmt);
        rbf_setFieldValue("price", total);

        $("input#vat, input#price").blur();
    }); 
}