Quick questions on Circular flow and national income - WJEC A-Level Economics

In the simplest two-sector model, all household income is spent on firms' output and all firm revenue is paid back to households, so the flow continues unchanged. The real economy is more complex because money leaks out of and is added to this loop. The model is the foundation of macroeconomics because it shows that one agent's spending is another's income, so a change anywhere ripples around the whole economy.

The multiplier is the ratio of the final change in national income ($\Delta Y$) to the initial change in injections ($\Delta J$). An initial injection becomes income for some households, who spend a fraction of it (the marginal propensity to consume, MPC), which becomes income for others, and so on. Because each round adds further spending, the total rise in income exceeds the initial injection. The size of the multiplier depends inversely on the marginal propensity to withdraw (MPW, the fraction of extra income saved, taxed or spent on imports): the more that leaks out at each round, the smaller the multiplier.

List the three injections and three withdrawals in the circular flow. [3 marks]

If the marginal propensity to withdraw is 0.25, calculate the multiplier. [2 marks]