A block is suspended using a rope $AB$ and a spring AC as shown. The spring is of stiffness $k=5000\frac{N}{m}$ and an unstretched $($initial$)$ length $L_0=0\mathrm{.}4m.$ Given $g=9\mathrm{.}81\frac{N}{k}g,$ if the block is in equilibrium in the position shown:

a$-$ The final length of the spring obtained from the figure is m

b$-$ The force in the spring is N

$c-$ The tension in rope $AB$ is N

d$-$ The mass of the block is kg