Help with JavaScript code for IF with a price range

Are there any ohter price ranges that you would apply different "salting rates" to? What if the Box A is set to 0? What if it's set to $10? What if it's set to $60? 

You might be able to make the necessary modifications yourself - try this as the custom calculation script for Box B:

// get the current value from "BoxA"

var boxA = this.getField("BoxA").value;
var thisValue = 0;
if (boxA == "" || boxA == 0) {
    thisValue = 0;
}
else if (boxA > 0 && boxA < 40) {
    thisValue = 5;
}
else if (boxA >= 40 && boxA <= 50) {
    thisValue = 30;
}
else {
    thisValue = 50;
}
event.value = thisValue;