The current I is defined as the amount of charge Q flowing through a certain point in a time t:
[tex]I= \frac{Q}{t} [/tex]
which can be rewritten as
[tex]Q=It[/tex]
so, by using this formula we can calculate the maximum amount of charge that can flow in the circuit. In fact, the maximum current is I=15 A, while the time is
[tex]t=24 h=86400 s[/tex]
so the maximum amount of charge is
[tex]Q=(15 A)(86400 s)=1.30 \cdot 10^6 C[/tex]
