Hi, could you please help me on this question?

7. In the Financial Times' article "Fed signals no rate rise until at least 2024 despite growth upgrade" (17 March 2021), we can read: "Federal Reserve officials signalled that they expect to keep interest rates close to zero until at least 2024, even as they sharply upgraded their US growth forecasts because of a massive fiscal stimulus and an accelerating vaccine rollout. [...] The upgrades to the forecasts from Fed officials were significant: whereas in December they predicted 4.2 per cent growth this year, that estimate was bumped up to 6.5 per cent, which would be the fastest economic expansion since 1984. Meanwhile, the unemployment rate is now forecast to fall to 4.5 per cent by the end of the year instead of 5 per cent. [...] inflation [...], is expected to rise to 2.2 per cent and above the central bank's 2 per cent target, compared with the smaller rise to 1.8 per cent predicted in December. [...] The Fed has pledged to maintain rock-bottom interest rates until the US reaches full employment, with inflation hitting 2 per cent and being on track to exceed that target." (a) Represent the US economy in a three-equation model. (5 marks)(b) Explain how the fiscal stimulus affect the economy, the potential multiplier effect of this stimulus considering the US current situation, and the potential limitations (if any) of the US policy mix adopted. (20 marks, 300 words max)