Question

Can someone please help ? Thank you

Answer 1

a) after 40 mins plan A costs $4 and plan B costs $8, so plan A costs less, by $4

b) at 140 mins the plans cost the same. If the time spent is less than 140 mins plan A would cost less

So basically answers are:
Plan A
$4
140
Plan A

Answer 2

I am not sure but I think Plan B is less. In my opinion.