calculate_price_excluding _VAT.js

// Description:
// Write a function that calculates the original product price, without VAT.
// Example
// If a product price is 200.00 and VAT is 15%, then the final product price (with VAT) is: 200.00 + 15% = 230.00
// Thus, if your function receives 230.00 as input, it should return 200.00
// Notes:
// VAT is always 15% for the purposes of this Kata.
// Round the result to 2 decimal places.
// If null value given then return -1

// SOLUTION:

const  excludingVatPrice = price => price === null? -1 : price - price * 15 / 115;