What is the byte capacity of a drum which is 5 inch high, 10 inch diameter, and which has 60 tracks per inch and bit density of 800 bits per inch?

Answer: Option A

The byte capacity of a drum which is 5 inch high, 10 inch diameter, and which has 60 tracks per inch and bit density of 800 bits per inch,
Total capacity = (areal density) x (total surface area)
Areal density = 60 x 800 = 48000 bits per inch
Total surface area = 2πrh = 2 × π × 5 × 5 = 50π
Total capacity = $$\frac{\left(50\times 3.14\times 48000\right)}{8}$$     = 942000 bytes.