Answer :
The type of control chart that is best to monitor this process is C-chart.
Explanation:
C-chart helps in determining whether the defects or returns are within the control limits or not.
Given:
Mean = average = 6 per day
Z=3
UcL = mean + 3[square root of mean]
= 6 + 3 (Sq root of 6)
UcL = 13.34
LcL= mean - 3[ square foot of mean] = - 1.34
LcL= -1.34
So the returns are within the control limits.