​Thirty-five samples of size 7 each were taken from a​ fertilizer-bag-filling machine at Panos Kouvelis Lifelong Lawn Ltd. The results​ were: Overall mean​ = 54.75 ​lb.; Average range R ​= 1.64 lb.

For the given sample​ size, the control limits for ​3-sigma x chart ​are: _________