How to create a condition?

Question

JavaScript

I am making a calculator and it is necessary to make a condition if the variable B>1, then to the value +100 +200 +300.
Simply put, the delivery slider, the first kilometer is 2500 rubles, the subsequent +100 rubles.

Answer 1

(A * 4500) + (B + 2500) + result()
function result() {
  if (B > 1) {
    B + 100
  } else {
    B + 0
  }
}

Answer 2

let a = 1,
b = 1,
d = 0,
res;
if (b > 1) {
b += 100
} else {
b = 0
}
res = ( a * 4500) + (b + 2500) + d