please help and explain

8) [4 points] For the following instruction sequence show the bubbles required to ensure correct output without reordering and without forwarding paths. Draw arrows representing the flow of r3 and r4. [See figures 4.53 and 4.58] and r3, rl, r2 lw r4, 10 (r3) sub r5, r4, rl Instr CC1 CC2 CC4 CC5 CC6CC7 CC8 IM RF IM RF DM IM RF DM IM DM IM DM RF IM DM RF