An automatic machine turns out round-head bolts with a specified shank diameter of 9.00 +-0.04 mm. The process has been operating in control at an estimated (Average) of 9.0 mm and an (R-bar) of 0.0206 mm. The subgroup size is four. Calculate the control limits for R chart. R-chart UCL = D4 x R-bar LCL = D3 x R-bar Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a UCL is 0.0529 mm and LCL is 0.0000 mm b UCL is 0.0435 mm and LCL is 0.0016 mm c UCL is 0.0673 mm and LCL is 0.0029 mm d UCL is 0.0469 mm and LCL is 0.0000 mm