A spring hanging vertically under its own weight has length 54 cm. When

a 6.1 kg mass is attached to the end of it, it stretches vertically so that its

new length is 109 cm when hanging at rest. If we remove the 6.1 kg

mass, attach a 14.4 kg mass to the end of the spring, and again allow it

to hang vertically, how long will the spring be? Express your answer in

cm.