The diagram illustrates a junction in a circuit at which three wires $P$, $Q$ and $R$ join. The currents in $P$ and $Q$ are $1\,\text{A}$ and $3\,\text{A}$, respectively, in the directions indicated. What quantity of charge flows past a fixed point in wire $R$ during a time of $5\,\text{s}$?
- A$0.4\,\text{C}$
- B$2\,\text{C}$
- C$10\,\text{C}$
- D$20\,\text{C}$