Can someone tell me if this looks right and the accounts receivable turnover ratio

Accounts Receivable Turnover Ratio 2014 2015 2016 2017 Gross Sales (after Trade Discounts) 416,713.51 407,642.05 538,691.19 634,827.92 Less: Allowance for Sales Returns (Gross Sales x 4%) 16,668.54 16,305.68 21,547.65 25,393.12 Net Sales 400,044.97 391,336.37 517,143.55 609,434.80 Gross Ending A/R Allowance (Gross A/Rx 1.5%) Net Ending A/R 110,909.87 108,495.47 143,374.69 168,961.84 1,663.65 1,627,43 2,150.62 2,534.43 109,246.22 106,868.04 141,224.07 166,427.41 Accounts Receivable Turnover Ratio N/A