Weight of water displaced = upthrust = 30 - 21 = 9N
Mass of water displaced = 910\frac{9}{10}109 = 0.9kg
Volume of object = 9 × 10−4^{-4}−4m3^{3}3
= (9 × 10−4^{-4}−4) (1.4 ×103)
= 1.26kg = 12N
30 - 12.6 = 17.4N
