So,
From the graph, we can clearly state that:
In 2 mins, there were 0 calls.
In 3 mins, there was 1 call.
In 4 mins, there were 4 calls.
In 5 mins, there were 6 calls.
In 6 mins, there were 4 calls.
Then, the number of calls that were answered to in 6 mins or less were 0+1+4+6+4 = 15
