Oil in hydraulic cylinder is compressed from an initial volume 2m3 to 1.96 m3. If the pressure of oil in the cylinder changes from 40 MPa to 80 MPa during compression, the bulk modulus of elasticity of oil is_________
(a) 1000 MPa (b) 2000 MPa
(c) 4000 MPa (d) 8000 MPa