(a) Let the oil layer be x cm deep. Then weight of block = weight of oil displaced + weight of water displaced.

or (10^{3} )(0.5) = 10^{2} (x) (0.8) g + 10^{2} (6 – x) 1

or x = 5 cm.

(b) Gauge pressure at the lower face of the block

= 5 × 0.8 × 98 + 1 × 1 × 980

= 4900 dynes/cm^{2 }.