If I understand what you're trying to achieve, the custom calculation script for the text field could be:
// Custom calculation script for text field
(function () {
// Get the field values
var v1 = getField("CHESTQTY").value;
var v2 = getField("BACKQTY").value;
// Create a variable for the sum
var sum = 0;
// Add 35 to the sum if any of the radio buttons is selected
if (v1 !== "Off") sum += 35;
// Add 85 to the sum if any of the other radio buttons is selected
if (v2 !== "Off") sum += 85;
// Set this field's value to the sum
event.value = sum;
})();