Answer
given,
height of water = 28 cm
specific gravity of the oil = 0.78
new height of the water level = 34 cm
height of water = ?
increase in height = 34 - 28 = 6 cm
water oil interface is at = 28 - 6 = 22 cm
so, now, 12 cm of weight of water is to be displaced by oil
height of the equivalent oil
= 12 / 0.78
= 15.38 cm
height of the oil from the bottom is equal to
= 22 + 15.38
= 37.38 cm