Particle on light elastic thread answer not matching

[ssadi]

My problem in (ii) find the mass of the particle. My answer comes as 0.54 kg whereas the answer is given as 1.98 kg.
My working: EPE gained=(1.5*2-(2.4))*.5*90=27
KE=.5*m*10^2
thus m=.54
Mark scheme:


I think the mark scheme is wrong as the wire was prestreched by (2.4-1.6)m as shown in the diagram. But mark schemes are rarely wrong. Can you point out the fault in my reasoning? Thanks for reading.

[skeeter]

initial stretch ... m

final stretch ... m







kg

[ssadi]

initial stretch ... m

final stretch ... m







kg

Thanks, rather silly mistake I see me do.