Real time system means that the system is subjected to real time, i.e., response should be guaranteed within a specified timing constraint or system should meet the specified deadline. For example: flight control system, real time monitors etc.
Answer:
Q=It
and
p=IV
Given, v=9V P= 7W
I=P/V
I =7/9
Also, time(t) from 9am to 12pm is 3hrs
Converting into sec =3×3600
t=10800
Q= 7/9 ×10800
Q =8400C
The answer you're looking for might be "backwards-compatible".
Optima battery because it is stronger than a factory battery