Please help with all parts asap. Problem $4$: Work and Energy

The figure below shows a block of mass $m=20\mathrm{.}0kg$ released from rest at height $h=1\mathrm{.}20m$ above the ground, directly over a spring of length $L=0\mathrm{.}350m.$

a$)$ Prove that when the block reaches height $L,$ its speed is $4\mathrm{.}08\frac{m}{s}.$

b$)$ Suppose the block lands on the spring, and compresses the spring until the block comes to rest at height $0\mathrm{.}100m.$ Prove that the spring has spring constant $k=6\mathrm{.}90{10}^3\frac{N}{m}.$

c$)$ Prove that the total work done on the block during the spring's compression is $-167J.$ Provide a physical explanation for why this work is negative.