What was the content of a single tablet if the A1%,1cm was 490?

20 Carbamazepine tablets were found to weigh 10.000g in total. The tablets were ground to a fine powder using a pestle and mortar. A 0.3000g sample of the powder was boiled with 25ml ethanol for a few minutes. The hot mixture was stirred in a closed flask for 10 minutes and filtered through sintered glass. The flask and filter were washed with ethanol and the washings combined with the filtrate. The cooled mixture was made up to 100ml with ethanol. 5ml of the ethanol extract was diluted to 250ml with ethanol and the absorbance of the resulting solution was found to be 0.588 absorbance units at a wavelength of 285nm.