A block is suspended using a rope $AB$ and a spring $AC$ as shown. The spring is of stiffness $k=500\frac{N}{m}$ and an unstretched $($initial$)$ length $L_0=0\mathrm{.}3m.$ 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 $$

b$-$ The force in the spring is $$ N

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

d$-$ The mass of the block is $$