“Point P is the junction of three capacitors: $6\ \mu\text{F}$ to a terminal at $50\ \text{V}$, $4\ \mu\text{F}$ to a terminal at $20\ \text{V}$, and $2\ \mu\text{F}$ to a terminal at $-10\ \text{V}$. No other wire is joined to P. What is the potential of P?” is available to Standard subscribers.