sign_shop.rb

def add_tax(cost, tax_rate)
  price + (price * tax_rate)
end


def sign_cost(height, width, color_count)
  subtotal = height * width * 15
  color_modifier = (color_count <= 2) ? 10 : 15
  subtotal += subtotal * color_modifier
  total = add_tax(subtotal, 0.15)
end