# Linear APR model



The linear APR model is a pricing model for a Principal Token quoted in underlying. It assumes that the price of the PT is a unit of underlying discounted by a non-compounded implied rate that stays constant during the term. More specifically, is assumes

$$
P(t,T) =\text{PT.previewRedeem(1)}\frac{1}{1+r(T-t)}
$$

where $\text{previewRedeem(1)}$ gives the redemption rate of the PT,  `T` is the maturity timestamp, while `t` is the current timestamp.