Edrey Ching wrote: Its like this, a user will select first ...
You are explaining the problem, not the solution.
Let me ask in another way:
If Maths is 8am to 10am
Explain why following wont work:
1. English at 7am to 9am
2. English at 9am to 11am
3. English at 8am to 10am
4. English at 8:30am to 9:30am