The graph below shows the total number of cars painted by two different robots, Robot A and Robot B over a period of 10 hours at a constant rate. Robot B stopped working after 5 hours while Robot A continued painting the cars at the same constant rate as before.

1. Identify the time when Robot B stopped working

From the question, Robot B stopped working after 5 hours.

2. Read the total number of cars painted at 5 hours from the graph

At $t = 5$ hours, the graph shows the total number of cars painted is $50$.

1. Find the number of cars painted by Robot A alone in the last 5 hours

From the graph, the total number of cars painted at 5 hours is $50$, and at 10 hours is $85$.
Number of cars painted by Robot A from 5 to 10 hours = $85 - 50 = 35$

2. Calculate the total number of cars painted by Robot A over the 10 hours

Since Robot A paints at a constant rate, the number of cars it paints in 10 hours is twice the amount it paints in 5 hours.
Total cars painted by Robot A = $35 \times 2 = 70$