Can someone help me with the formula needed to obtain the following. I need to discount products on a sliding scale. If a customer purchases 2 products, he must get a 15% discount. If he purchases 10, he must get a 30% discount. I don't want a linear slope, but rather as the number of products increases, the increase in the discount decreases.
2 => 15% 4 => ≈20% 10 => 30%
I need to formula with this, which should include a bend factor.
I know how do to this for FV, IV, but not this.