# fCash Valuation Curve

The present value of fCash can be determined by discounting the face value of that fCash to the present via the oracle rate which corresponds to the fCash asset's maturity.

$PV(fCash) = fCash * e^{-oracleRate * timeToMaturity}$

The active set of rate oracles for a given currency provide explicit interest rates with which to value fCash assets at the corresponding maturity set.

Determining the present value of an fCash asset requires an interest rate to the fCash asset's maturity. But by definition, idiosyncratic fCash assets do not correspond to a maturity within the rate oracle set, so interest rates for idiosyncratic fCash assets are not immediately available. We solve this problem by drawing a fCash valuation curve that is linearly interpolated from our available rate oracles and then picking interest rates from that curve at any idiosyncratic maturity.

The interest rates derived from the fCash valuation curve then enable us to determine the present value of any idiosyncratic fCash asset by the formula detailed above.

Upon the quarterly roll, the maturities of the interest rate oracles update to match the new set of active maturities. The new interest rate oracle values are updated to match the rates defined by the old interest rate curve at the new active maturities.

Rolling the curve in this way ensures consistency. The new interest rate oracle values are implied from the old curve, and interest rates associated with the old active maturity set remain constant.