A firm had a total COGS of $1265 M (Data per quarter: 280, 295, 340, & 350, respectively). The raw material inventory at the end of each quarter was 50,40,55, &60, respectively. The company reported that it used $500 M worth of raw material during the year. On average, how many weeks of supply of raw material are on hand at the factory? Please provide detailed calculations and explanation.