# 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.


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