Past exam of the mathematics course of the University of Cambridge / 2021 / iii / Paper 202 / 6 / a

An $x$-admissible strategy is a predictable vector of holdings $\varphi =({\varphi }^0,\dots ,{\varphi }^d)$ that is integrable against the asset prices, is self-financing, has initial wealthand whose wealth process $V_t={\sum }_i{\varphi }_t^i{S}_t^i$ remains nonnegative.