Hi,Sarah did 12 km (exactly) from 10 am to 11 am - so (I know you got it right as you say), velocity = (v simple maths even for a millennial [who normally automatically reaches for a calculator] - sorry!) 12 kph.
She continued for 3 km (at the same velocity) (3 is a quarter of 12, so it took her a quarter of one hour = 15 minutes extra past her home.
The graph shows that she took a 30 min break from 11 to 11.30 am;
So, the time back home = 1 hour (as on way out plus the 15 min mentioned above = 1 hr 15 min
From 11.30 am if you add this 75 min you get 12.45 pm.
However, this is an ambiguous Q because technically Sarah would have passed her home BEFORE doing the extra 3 km, so the answer should be 15 min less = 12.30 pm (but that would be too simple, I suppose!!) I would guess that if they are as incompetent in physics as they are in biology, THIS IS AN EDEXCEL Q
[do let me know, pls!)
M.