When a block of iron floats in mercury at 0∘C , fraction k1 of its volume is submerged, while at the temperature 60∘C , a fraction k2 is seen to be submerged. If the coefficient of volume expansion of iron is γFe and that of mercury is γHg , then the ratio k1/k2 can be expressed as
a. 1+60γHg1+60γFe
b. 1+60γHg1−60γFe
c. 1−60γHg1+60γFe
d. 1+60γFe1+60γHg